diff --git a/composer.json b/composer.json
index 06edbbf0e776d..789c7220954b2 100644
--- a/composer.json
+++ b/composer.json
@@ -53,6 +53,7 @@
 		"phpcompatibility/phpcompatibility-wp": "~2.1.3",
 		"phpstan/phpstan": "2.2.13",
 		"phpstan/phpstan-phpunit": "2.0.18",
+		"szepeviktor/phpstan-wordpress": "^2.0.4",
 		"yoast/phpunit-polyfills": "^1.1.0"
 	},
 	"config": {
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index cc4579365122b..b1240bc16b1f7 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -54,7 +54,6 @@ includes:
 	- tests/phpstan/baselines/isset.offset.neon
 	- tests/phpstan/baselines/isset.property.neon
 	- tests/phpstan/baselines/method.childParameterType.neon
-	- tests/phpstan/baselines/method.nonObject.neon
 	- tests/phpstan/baselines/method.unused.neon
 	- tests/phpstan/baselines/notIdentical.alwaysTrue.neon
 	- tests/phpstan/baselines/nullCoalesce.offset.neon
@@ -62,7 +61,6 @@ includes:
 	- tests/phpstan/baselines/offsetAccess.nonOffsetAccessible.neon
 	- tests/phpstan/baselines/offsetAccess.notFound.neon
 	- tests/phpstan/baselines/offsetAssign.valueType.neon
-	- tests/phpstan/baselines/parameter.defaultValue.neon
 	- tests/phpstan/baselines/parameter.notFound.neon
 	- tests/phpstan/baselines/parameter.phpDocType.neon
 	- tests/phpstan/baselines/parameterByRef.type.neon
diff --git a/src/wp-admin/customize.php b/src/wp-admin/customize.php
index 75c0865b1f8eb..332d7cfc9f13a 100644
--- a/src/wp-admin/customize.php
+++ b/src/wp-admin/customize.php
@@ -110,8 +110,10 @@
 $wp_scripts             = new WP_Scripts();
 $wp_scripts->registered = $registered;
 
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'customize_controls_print_scripts', 'print_head_scripts', 20 );
 add_action( 'customize_controls_print_footer_scripts', '_wp_footer_scripts' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'customize_controls_print_styles', 'print_admin_styles', 20 );
 
 /**
diff --git a/src/wp-admin/includes/admin-filters.php b/src/wp-admin/includes/admin-filters.php
index 5337cc02c88c9..3f619d5df2664 100644
--- a/src/wp-admin/includes/admin-filters.php
+++ b/src/wp-admin/includes/admin-filters.php
@@ -11,6 +11,7 @@
 add_action( 'admin_page_access_denied', 'wp_link_manager_disabled_message' );
 
 // Dashboard hooks.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'activity_box_end', 'wp_dashboard_quota' );
 add_action( 'welcome_panel', 'wp_welcome_panel' );
 
@@ -18,9 +19,13 @@
 add_action( 'attachment_submitbox_misc_actions', 'attachment_submitbox_metadata' );
 add_filter( 'plupload_init', 'wp_show_heic_upload_error' );
 
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'media_upload_image', 'wp_media_upload_handler' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'media_upload_audio', 'wp_media_upload_handler' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'media_upload_video', 'wp_media_upload_handler' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'media_upload_file', 'wp_media_upload_handler' );
 
 add_action( 'post-plupload-upload-ui', 'media_upload_flash_bypass' );
@@ -57,10 +62,12 @@
 }
 
 add_action( 'admin_print_scripts', 'print_emoji_detection_script' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_print_scripts', 'print_head_scripts', 20 );
 add_action( 'admin_print_footer_scripts', '_wp_footer_scripts' );
 add_action( 'admin_enqueue_scripts', 'wp_enqueue_emoji_styles' );
 add_action( 'admin_print_styles', 'print_emoji_styles' ); // Retained for backwards-compatibility. Unhooked by wp_enqueue_emoji_styles().
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_print_styles', 'print_admin_styles', 20 );
 
 add_action( 'admin_print_scripts-index.php', 'wp_localize_community_events' );
@@ -130,10 +137,12 @@
 add_action( 'load-plugins.php', 'wp_plugin_update_rows', 20 ); // After wp_update_plugins() is called.
 add_action( 'load-themes.php', 'wp_theme_update_rows', 20 ); // After wp_update_themes() is called.
 
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_notices', 'update_nag', 3 );
 add_action( 'admin_notices', 'deactivated_plugins_notice', 5 );
 add_action( 'admin_notices', 'paused_plugins_notice', 5 );
 add_action( 'admin_notices', 'paused_themes_notice', 5 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_notices', 'maintenance_nag', 10 );
 add_action( 'admin_notices', 'wp_recovery_mode_nag', 1 );
 
diff --git a/src/wp-admin/includes/bookmark.php b/src/wp-admin/includes/bookmark.php
index c64bac144c588..f8f8dd68b291b 100644
--- a/src/wp-admin/includes/bookmark.php
+++ b/src/wp-admin/includes/bookmark.php
@@ -12,6 +12,8 @@
  * @since 2.0.0
  *
  * @return int The link ID on success. The value 0 on failure.
+ *
+ * @phpstan-return int<0, max>
  */
 function add_link() {
 	return edit_link();
@@ -24,6 +26,8 @@ function add_link() {
  *
  * @param int $link_id Optional. ID of the link to edit. Default 0.
  * @return int The link ID on success. The value 0 on failure.
+ *
+ * @phpstan-return int<0, max>
  */
 function edit_link( $link_id = 0 ) {
 	if ( ! current_user_can( 'manage_links' ) ) {
@@ -56,6 +60,9 @@ function edit_link( $link_id = 0 ) {
  * @since 2.0.0
  *
  * @return stdClass Default link object.
+ *
+ * @phpstan-impure
+ * @phpstan-return object{link_url: string, link_name: string, link_visible: 'Y'}&stdClass
  */
 function get_default_link_to_edit() {
 	$link = new stdClass();
@@ -122,6 +129,8 @@ function wp_delete_link( $link_id ) {
  *
  * @param int $link_id Link ID to look up.
  * @return int[] The IDs of the requested link's categories.
+ *
+ * @phpstan-return ($link_id is empty ? array{} : array<int, int<1, max>>)
  */
 function wp_get_link_cats( $link_id = 0 ) {
 	$cats = wp_get_object_terms( $link_id, 'link_category', array( 'fields' => 'ids' ) );
@@ -170,6 +179,8 @@ function get_link_to_edit( $link ) {
  * }
  * @param bool  $wp_error Optional. Whether to return a WP_Error object on failure. Default false.
  * @return int|WP_Error The link ID on success. The value 0 or WP_Error on failure.
+ *
+ * @phpstan-return ($wp_error is false ? int<0, max> : int<0, max>|WP_Error)
  */
 function wp_insert_link( $linkdata, $wp_error = false ) {
 	global $wpdb;
@@ -296,6 +307,8 @@ function wp_set_link_cats( $link_id = 0, $link_categories = array() ) {
  *
  * @param array $linkdata Link data to update. See wp_insert_link() for accepted arguments.
  * @return int The updated link ID on success. The value 0 on failure.
+ *
+ * @phpstan-return int<0, max>
  */
 function wp_update_link( $linkdata ) {
 	$link_id = (int) $linkdata['link_id'];
diff --git a/src/wp-admin/includes/class-custom-background.php b/src/wp-admin/includes/class-custom-background.php
index 7f8f23485086a..7e318658da48b 100644
--- a/src/wp-admin/includes/class-custom-background.php
+++ b/src/wp-admin/includes/class-custom-background.php
@@ -19,6 +19,8 @@ class Custom_Background {
 	 *
 	 * @since 3.0.0
 	 * @var callable
+	 *
+	 * @phpstan-var ''|callable(): void
 	 */
 	public $admin_header_callback;
 
@@ -27,6 +29,8 @@ class Custom_Background {
 	 *
 	 * @since 3.0.0
 	 * @var callable
+	 *
+	 * @phpstan-var ''|callable(): void
 	 */
 	public $admin_image_div_callback;
 
@@ -47,6 +51,9 @@ class Custom_Background {
 	 *                                           Default empty string.
 	 * @param callable $admin_image_div_callback Optional. Custom image div output callback.
 	 *                                           Default empty string.
+	 *
+	 * @phpstan-param ''|callable(): void $admin_header_callback
+	 * @phpstan-param ''|callable(): void $admin_image_div_callback
 	 */
 	public function __construct( $admin_header_callback = '', $admin_image_div_callback = '' ) {
 		$this->admin_header_callback    = $admin_header_callback;
diff --git a/src/wp-admin/includes/class-custom-image-header.php b/src/wp-admin/includes/class-custom-image-header.php
index c1816ffae2d9c..de0e8932714f7 100644
--- a/src/wp-admin/includes/class-custom-image-header.php
+++ b/src/wp-admin/includes/class-custom-image-header.php
@@ -19,6 +19,8 @@ class Custom_Image_Header {
 	 *
 	 * @since 2.1.0
 	 * @var callable
+	 *
+	 * @phpstan-var ''|callable(): void
 	 */
 	public $admin_header_callback;
 
@@ -27,6 +29,8 @@ class Custom_Image_Header {
 	 *
 	 * @since 3.0.0
 	 * @var callable
+	 *
+	 * @phpstan-var ''|callable(): void
 	 */
 	public $admin_image_div_callback;
 
@@ -54,6 +58,8 @@ class Custom_Image_Header {
 	 * @param callable $admin_header_callback    Administration header callback.
 	 * @param callable $admin_image_div_callback Optional. Custom image div output callback.
 	 *                                           Default empty string.
+	 *
+	 * @phpstan-param ''|callable(): void $admin_image_div_callback
 	 */
 	public function __construct( $admin_header_callback, $admin_image_div_callback = '' ) {
 		$this->admin_header_callback    = $admin_header_callback;
@@ -310,6 +316,8 @@ public function process_default_headers() {
 	 *
 	 * @param string $type The header type. One of 'default' (for the Uploaded Images control)
 	 *                     or 'uploaded' (for the Uploaded Images control).
+	 *
+	 * @phpstan-param 'default'|'uploaded' $type
 	 */
 	public function show_header_selector( $type = 'default' ) {
 		if ( 'default' === $type ) {
@@ -1169,6 +1177,13 @@ public function filter_upload_tabs( $tabs ) {
 	 *                      registered for that theme; and the key of an image uploaded for that theme
 	 *                      (the attachment ID of the image). Or an array of arguments: attachment_id,
 	 *                      url, width, height. All are required.
+	 *
+	 * @phpstan-param string|array{
+	 *     attachment_id: int<1, max>,
+	 *     url: string,
+	 *     width: int<0, max>,
+	 *     height: int<0, max>,
+	 * } $choice
 	 */
 	final public function set_header_image( $choice ) {
 		if ( is_array( $choice ) || is_object( $choice ) ) {
diff --git a/src/wp-admin/includes/class-wp-comments-list-table.php b/src/wp-admin/includes/class-wp-comments-list-table.php
index 2b927a7f81a6a..7294f89d1bd3b 100644
--- a/src/wp-admin/includes/class-wp-comments-list-table.php
+++ b/src/wp-admin/includes/class-wp-comments-list-table.php
@@ -62,6 +62,8 @@ public function __construct( $args = array() ) {
 	 * @param string $name       Comment author name.
 	 * @param int    $comment_id Comment ID.
 	 * @return string Avatar with the user name.
+	 *
+	 * @phpstan-return non-falsy-string
 	 */
 	public function floated_admin_avatar( $name, $comment_id ) {
 		$comment = get_comment( $comment_id );
diff --git a/src/wp-admin/includes/class-wp-list-table.php b/src/wp-admin/includes/class-wp-list-table.php
index df8e71834e0db..84f69c1f4c511 100644
--- a/src/wp-admin/includes/class-wp-list-table.php
+++ b/src/wp-admin/includes/class-wp-list-table.php
@@ -319,6 +319,9 @@ public function prepare_items() {
 	 * @since 3.1.0
 	 *
 	 * @param array|string $args Array or string of arguments with information about the pagination.
+	 *
+	 * @phpstan-param array{total_items?: int, total_pages?: int, per_page?: int} $args
+	 * @phpstan-return void
 	 */
 	protected function set_pagination_args( $args ) {
 		$args = wp_parse_args(
diff --git a/src/wp-admin/includes/class-wp-posts-list-table.php b/src/wp-admin/includes/class-wp-posts-list-table.php
index d3d631b9b4467..9957a765dde47 100644
--- a/src/wp-admin/includes/class-wp-posts-list-table.php
+++ b/src/wp-admin/includes/class-wp-posts-list-table.php
@@ -1856,7 +1856,7 @@ public function inline_edit() {
 							 * @param array $users_opt An array of arguments passed to wp_dropdown_users().
 							 * @param bool  $bulk      A flag to denote if it's a bulk action.
 							 */
-							$users_opt = apply_filters( 'quick_edit_dropdown_authors_args', $users_opt, $bulk );
+							$users_opt = apply_filters( 'quick_edit_dropdown_authors_args', $users_opt, (bool) $bulk );
 
 							$authors = wp_dropdown_users( $users_opt );
 
@@ -1961,7 +1961,7 @@ public function inline_edit() {
 							 * @param array $dropdown_args An array of arguments passed to wp_dropdown_pages().
 							 * @param bool  $bulk          A flag to denote if it's a bulk action.
 							 */
-							$dropdown_args = apply_filters( 'quick_edit_dropdown_pages_args', $dropdown_args, $bulk );
+							$dropdown_args = apply_filters( 'quick_edit_dropdown_pages_args', $dropdown_args, (bool) $bulk );
 
 							wp_dropdown_pages( $dropdown_args );
 							?>
@@ -2108,12 +2108,12 @@ public function inline_edit() {
 								 *
 								 * @since 6.9.0
 								 *
-								 * @param array<string,string> $inline_edit_statuses An array of statuses available in the Quick Edit UI.
-								 * @param string               $post_type            The post type slug.
-								 * @param bool                 $bulk                 A flag to denote if it's a bulk action.
-								 * @param bool                 $can_publish          A flag to denote if the user can publish posts.
+								 * @param string[] $inline_edit_statuses An array of statuses available in the Quick Edit UI.
+								 * @param string   $post_type            The post type slug.
+								 * @param bool     $bulk                 A flag to denote if it's a bulk action.
+								 * @param bool     $can_publish          A flag to denote if the user can publish posts.
 								 */
-								$inline_edit_statuses = apply_filters( 'quick_edit_statuses', $inline_edit_statuses, $screen->post_type, $bulk, $can_publish );
+								$inline_edit_statuses = apply_filters( 'quick_edit_statuses', $inline_edit_statuses, $screen->post_type, (bool) $bulk, $can_publish );
 
 								foreach ( $inline_edit_statuses as $inline_status_value => $inline_status_text ) :
 									?>
diff --git a/src/wp-admin/includes/class-wp-upgrader.php b/src/wp-admin/includes/class-wp-upgrader.php
index ba27113ff73de..2005c1e231dd8 100644
--- a/src/wp-admin/includes/class-wp-upgrader.php
+++ b/src/wp-admin/includes/class-wp-upgrader.php
@@ -933,6 +933,7 @@ public function run( $options ) {
 				 * internally during actions, causing an error because
 				 * `WP_Upgrader::restore_temp_backup()` expects an array.
 				 */
+				// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 				add_action( 'shutdown', array( $this, 'restore_temp_backup' ), 10, 0 );
 			}
 			$this->skin->error( $result );
@@ -950,6 +951,7 @@ public function run( $options ) {
 		// Clean up the backup kept in the temporary backup directory.
 		if ( ! empty( $options['hook_extra']['temp_backup'] ) ) {
 			// Delete the backup on `shutdown` to avoid a PHP timeout.
+			// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 			add_action( 'shutdown', array( $this, 'delete_temp_backup' ), 100, 0 );
 		}
 
diff --git a/src/wp-admin/includes/dashboard.php b/src/wp-admin/includes/dashboard.php
index 488e01aa92481..aafcaa9ac503b 100644
--- a/src/wp-admin/includes/dashboard.php
+++ b/src/wp-admin/includes/dashboard.php
@@ -1622,7 +1622,7 @@ function wp_dashboard_primary() {
 			 *
 			 * @since 4.4.0
 			 *
-			 * @param string $items How many items to show in the secondary feed.
+			 * @param int $items How many items to show in the secondary feed.
 			 */
 			'items'        => apply_filters( 'dashboard_secondary_items', 3 ),
 			'show_summary' => 0,
diff --git a/src/wp-admin/includes/image.php b/src/wp-admin/includes/image.php
index 935c613d561e9..c3a4a8d769be0 100644
--- a/src/wp-admin/includes/image.php
+++ b/src/wp-admin/includes/image.php
@@ -635,7 +635,7 @@ function wp_generate_attachment_metadata( $attachment_id, $file ) {
 					break;
 			}
 			$basename = str_replace( '.', '-', wp_basename( $file ) ) . '-image' . $ext;
-			$uploaded = wp_upload_bits( $basename, '', $metadata['image']['data'] );
+			$uploaded = wp_upload_bits( $basename, null, $metadata['image']['data'] );
 			if ( false === $uploaded['error'] ) {
 				$image_attachment = array(
 					'post_mime_type' => $metadata['image']['mime'],
diff --git a/src/wp-admin/includes/list-table.php b/src/wp-admin/includes/list-table.php
index 97dfe4f858c7e..ed1fd61a40050 100644
--- a/src/wp-admin/includes/list-table.php
+++ b/src/wp-admin/includes/list-table.php
@@ -17,6 +17,15 @@
  * @param string $class_name The type of the list table, which is the class name.
  * @param array  $args       Optional. Arguments to pass to the class. Accepts 'screen'.
  * @return WP_List_Table|false List table object on success, false if the class does not exist.
+ *
+ * @phpstan-template T of string
+ * @phpstan-param T $class_name
+ * @phpstan-param array{screen?: string|WP_Screen|null} $args
+ * @phpstan-return (
+ *     $class_name is 'WP_Posts_List_Table'|'WP_Media_List_Table'|'WP_Terms_List_Table'|'WP_Users_List_Table'|'WP_Comments_List_Table'|'WP_Post_Comments_List_Table'|'WP_Links_List_Table'|'WP_Plugin_Install_List_Table'|'WP_Themes_List_Table'|'WP_Theme_Install_List_Table'|'WP_Plugins_List_Table'|'WP_Application_Passwords_List_Table'|'WP_MS_Sites_List_Table'|'WP_MS_Users_List_Table'|'WP_MS_Themes_List_Table'|'WP_Privacy_Data_Export_Requests_List_Table'|'WP_Privacy_Data_Removal_Requests_List_Table'
+ *         ? new<T>
+ *         : false
+ * )
  */
 function _get_list_table( $class_name, $args = array() ) {
 	$core_classes = array(
diff --git a/src/wp-admin/includes/media.php b/src/wp-admin/includes/media.php
index be10d2f7bf0b6..09b244f3dbf11 100644
--- a/src/wp-admin/includes/media.php
+++ b/src/wp-admin/includes/media.php
@@ -211,9 +211,9 @@ function image_add_caption( $html, $id, $caption, $title, $align, $url, $size, $
 	 * @since 2.6.0
 	 *
 	 * @param bool $bool Whether to disable appending captions. Returning true from the filter
-	 *                   will disable captions. Default empty string.
+	 *                   will disable captions. Default false.
 	 */
-	if ( empty( $caption ) || apply_filters( 'disable_captions', '' ) ) {
+	if ( empty( $caption ) || apply_filters( 'disable_captions', false ) ) {
 		return $html;
 	}
 
@@ -1238,6 +1238,8 @@ function image_align_input_fields( $post, $checked = '' ) {
  * @param WP_Post     $post
  * @param bool|string $check
  * @return array<string, string> An array of data for the image size input fields.
+ *
+ * @phpstan-return array{label: string, input: 'html', html: string}
  */
 function image_size_input_fields( $post, $check = '' ) {
 	/**
@@ -1316,6 +1318,8 @@ function image_size_input_fields( $post, $check = '' ) {
  * @param WP_Post $post
  * @param string  $url_type
  * @return string HTML markup for the link URL buttons.
+ *
+ * @phpstan-return non-falsy-string
  */
 function image_link_input_fields( $post, $url_type = '' ) {
 
@@ -1349,6 +1353,8 @@ function image_link_input_fields( $post, $url_type = '' ) {
  *
  * @param WP_Post $edit_post Attachment WP_Post object.
  * @return string HTML markup for the textarea element.
+ *
+ * @phpstan-return non-falsy-string
  */
 function wp_caption_input_textarea( $edit_post ) {
 	// Post data is already escaped.
@@ -1638,6 +1644,8 @@ function get_media_items( $post_id, $errors ) {
  * @param int          $attachment_id Attachment ID for modification.
  * @param string|array $args          Optional. Override defaults.
  * @return string HTML form for attachment.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_media_item( $attachment_id, $args = null ) {
 	global $redir_tab;
@@ -1932,6 +1940,8 @@ function get_media_item( $attachment_id, $args = null ) {
  * @param int   $attachment_id
  * @param array $args
  * @return array<string, string> An array containing the media item and its metadata.
+ *
+ * @phpstan-return array{item: string, meta: string}
  */
 function get_compat_media_markup( $attachment_id, $args = null ) {
 	$post = get_post( $attachment_id );
@@ -3014,6 +3024,8 @@ function media_upload_library_form( $errors ) {
  *
  * @param string $default_view
  * @return string HTML content of the form.
+ *
+ * @phpstan-return non-falsy-string
  */
 function wp_media_insert_url_form( $default_view = 'image' ) {
 	/** This filter is documented in wp-admin/includes/media.php */
diff --git a/src/wp-admin/includes/menu.php b/src/wp-admin/includes/menu.php
index a95cf9e33956e..01bf5a046308b 100644
--- a/src/wp-admin/includes/menu.php
+++ b/src/wp-admin/includes/menu.php
@@ -208,6 +208,11 @@
  * @param string $class_to_add The CSS class to add.
  * @param string $classes      The string to add the CSS class to.
  * @return string The string with the CSS class added.
+ *
+ * @phpstan-template T of string
+ * @phpstan-param T $class_to_add
+ * @phpstan-pure
+ * @phpstan-return ($classes is empty ? T : non-empty-string)
  */
 function add_cssclass( $class_to_add, $classes ) {
 	if ( empty( $classes ) ) {
diff --git a/src/wp-admin/includes/meta-boxes.php b/src/wp-admin/includes/meta-boxes.php
index 535a00cd3fe94..9149f50daadd8 100644
--- a/src/wp-admin/includes/meta-boxes.php
+++ b/src/wp-admin/includes/meta-boxes.php
@@ -1257,6 +1257,8 @@ function link_target_meta_box( $link ) {
  *                                 if it matches the current link's relationship.
  *                                 Default empty string.
  * @param mixed  $deprecated       Deprecated. Not used.
+ *
+ * @phpstan-param '' $deprecated
  */
 function xfn_check( $xfn_relationship, $xfn_value = '', $deprecated = '' ) {
 	global $link;
diff --git a/src/wp-admin/includes/ms-admin-filters.php b/src/wp-admin/includes/ms-admin-filters.php
index b1d73825f1f4b..dd894ebfc72ea 100644
--- a/src/wp-admin/includes/ms-admin-filters.php
+++ b/src/wp-admin/includes/ms-admin-filters.php
@@ -29,11 +29,15 @@
 add_filter( 'import_allow_create_users', 'check_import_new_users' );
 
 // Notices hooks.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_notices', 'site_admin_notice' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'network_admin_notices', 'site_admin_notice' );
 
 // Update hooks.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'network_admin_notices', 'update_nag', 3 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'network_admin_notices', 'maintenance_nag', 10 );
 
 // Network Admin hooks.
diff --git a/src/wp-admin/includes/ms.php b/src/wp-admin/includes/ms.php
index 56e17113653d2..1bd642f704387 100644
--- a/src/wp-admin/includes/ms.php
+++ b/src/wp-admin/includes/ms.php
@@ -1186,6 +1186,8 @@ function network_edit_site_nav( $args = array() ) {
  * @since 4.9.0
  *
  * @return array Help tab arguments.
+ *
+ * @phpstan-return array{id: 'overview', title: string, content: non-falsy-string}
  */
 function get_site_screen_help_tab_args() {
 	return array(
@@ -1210,6 +1212,8 @@ function get_site_screen_help_tab_args() {
  * @since 4.9.0
  *
  * @return string Help sidebar content.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_site_screen_help_sidebar_content() {
 	return '<p><strong>' . __( 'For more information:' ) . '</strong></p>' .
diff --git a/src/wp-admin/includes/nav-menu.php b/src/wp-admin/includes/nav-menu.php
index f26d63d528e78..7eb8763b86cbe 100644
--- a/src/wp-admin/includes/nav-menu.php
+++ b/src/wp-admin/includes/nav-menu.php
@@ -1348,6 +1348,16 @@ function wp_get_nav_menu_to_edit( $menu_id = 0 ) {
  * @since 3.0.0
  *
  * @return string[] Array of column titles keyed by their column name.
+ *
+ * @phpstan-return array{
+ *     _title: string,
+ *     cb: '<input type="checkbox" />',
+ *     link-target: string,
+ *     title-attribute: string,
+ *     css-classes: string,
+ *     xfn: string,
+ *     description: string,
+ * }
  */
 function wp_nav_menu_manage_columns() {
 	return array(
diff --git a/src/wp-admin/includes/plugin-install.php b/src/wp-admin/includes/plugin-install.php
index 62e93a36eef5d..b780fa69c8e67 100644
--- a/src/wp-admin/includes/plugin-install.php
+++ b/src/wp-admin/includes/plugin-install.php
@@ -309,6 +309,8 @@ function install_dashboard() {
  * @since 4.6.0 The `$type_selector` parameter was deprecated.
  *
  * @param bool $deprecated Not used.
+ *
+ * @phpstan-param true $deprecated
  */
 function install_search_form( $deprecated = true ) {
 	$type = isset( $_REQUEST['type'] ) ? wp_unslash( $_REQUEST['type'] ) : 'term';
diff --git a/src/wp-admin/includes/plugin.php b/src/wp-admin/includes/plugin.php
index 9969316ab8d58..29a67dd8d5d0f 100644
--- a/src/wp-admin/includes/plugin.php
+++ b/src/wp-admin/includes/plugin.php
@@ -900,6 +900,9 @@ function activate_plugins( $plugins, $redirect = '', $network_wide = false, $sil
  * @param string   $deprecated Not used.
  * @return bool|null|WP_Error True on success, false if `$plugins` is empty, `WP_Error` on failure.
  *                            `null` if filesystem credentials are required to proceed.
+ *
+ * @phpstan-param '' $deprecated
+ * @phpstan-return ($plugins is empty ? false : true|null|WP_Error)
  */
 function delete_plugins( $plugins, $deprecated = '' ) {
 	global $wp_filesystem;
@@ -1105,6 +1108,8 @@ function validate_active_plugins() {
  *
  * @param string $plugin Path to the plugin file relative to the plugins directory.
  * @return int|WP_Error 0 on success, WP_Error on failure.
+ *
+ * @phpstan-return ($plugin is empty ? WP_Error : 0|WP_Error)
  */
 function validate_plugin( $plugin ) {
 	if ( validate_file( $plugin ) ) {
@@ -1388,6 +1393,8 @@ function uninstall_plugin( $plugin ) {
  *                              * Pass 'none' to leave div.wp-menu-image empty so an icon can be added via CSS.
  * @param int|float $position   Optional. The position in the menu order this item should appear.
  * @return string The resulting page's hook_suffix.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $icon_url = '', $position = null ) {
 	global $menu, $admin_page_hooks, $_registered_pages, $_parent_pages;
@@ -1483,6 +1490,8 @@ function add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $call
  * @param callable  $callback    Optional. The function to be called to output the content for this page.
  * @param int|float $position    Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	global $submenu, $menu, $_wp_real_parent_file, $_wp_submenu_nopriv,
@@ -1596,6 +1605,8 @@ function add_submenu_page( $parent_slug, $page_title, $menu_title, $capability,
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_management_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'tools.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1620,6 +1631,8 @@ function add_management_page( $page_title, $menu_title, $capability, $menu_slug,
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_options_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'options-general.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1644,6 +1657,8 @@ function add_options_page( $page_title, $menu_title, $capability, $menu_slug, $c
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_theme_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'themes.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1668,6 +1683,8 @@ function add_theme_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_plugins_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'plugins.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1692,6 +1709,8 @@ function add_plugins_page( $page_title, $menu_title, $capability, $menu_slug, $c
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_users_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	if ( current_user_can( 'edit_users' ) ) {
@@ -1721,6 +1740,8 @@ function add_users_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_dashboard_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'index.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1745,6 +1766,8 @@ function add_dashboard_page( $page_title, $menu_title, $capability, $menu_slug,
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_posts_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'edit.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1769,6 +1792,8 @@ function add_posts_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_media_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'upload.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1793,6 +1818,8 @@ function add_media_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_links_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'link-manager.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1817,6 +1844,8 @@ function add_links_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_pages_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'edit.php?post_type=page', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -1841,6 +1870,8 @@ function add_pages_page( $page_title, $menu_title, $capability, $menu_slug, $cal
  * @param callable $callback   Optional. The function to be called to output the content for this page.
  * @param int      $position   Optional. The position in the menu order this item should appear.
  * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
+ *
+ * @phpstan-param ''|callable $callback
  */
 function add_comments_page( $page_title, $menu_title, $capability, $menu_slug, $callback = '', $position = null ) {
 	return add_submenu_page( 'edit-comments.php', $page_title, $menu_title, $capability, $menu_slug, $callback, $position );
@@ -2136,6 +2167,8 @@ function get_plugin_page_hook( $plugin_page, $parent_page ) {
  * @param string $parent_page The slug name for the parent menu (or the file name of a standard
  *                            WordPress admin page).
  * @return string Hook name for the plugin page.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_plugin_page_hookname( $plugin_page, $parent_page ) {
 	global $admin_page_hooks;
diff --git a/src/wp-admin/includes/post.php b/src/wp-admin/includes/post.php
index 40a51e63945b3..2ce642cc2b02f 100644
--- a/src/wp-admin/includes/post.php
+++ b/src/wp-admin/includes/post.php
@@ -1206,6 +1206,8 @@ function _fix_attachment_links( $post ) {
  *
  * @param string $type The post_type you want the statuses for. Default 'post'.
  * @return string[] An array of all the statuses for the supplied post type.
+ *
+ * @phpstan-return list<string>
  */
 function get_available_post_statuses( $type = 'post' ) {
 	$statuses = wp_count_posts( $type );
diff --git a/src/wp-admin/includes/taxonomy.php b/src/wp-admin/includes/taxonomy.php
index 470d36d55ffb1..85c7095183d7c 100644
--- a/src/wp-admin/includes/taxonomy.php
+++ b/src/wp-admin/includes/taxonomy.php
@@ -117,6 +117,8 @@ function wp_create_categories( $categories, $post_id = 0 ) {
  * @param bool  $wp_error Optional. Default false.
  * @return int|WP_Error The ID number of the new or updated Category on success. Zero or a WP_Error on failure,
  *                      depending on param `$wp_error`.
+ *
+ * @phpstan-return ($wp_error is false ? int<0, max> : int<1, max>|WP_Error)
  */
 function wp_insert_category( $catarr, $wp_error = false ) {
 	$cat_defaults = array(
@@ -184,6 +186,8 @@ function wp_insert_category( $catarr, $wp_error = false ) {
  *
  * @param array $catarr The 'cat_ID' value is required. All other keys are optional.
  * @return int|false The ID number of the new or updated Category on success. Zero or FALSE on failure.
+ *
+ * @phpstan-return int<0, max>|false
  */
 function wp_update_category( $catarr ) {
 	$cat_id = (int) $catarr['cat_ID'];
@@ -218,6 +222,12 @@ function wp_update_category( $catarr ) {
  * @return mixed Returns null if the term does not exist.
  *               Returns an array of the term ID and the term taxonomy ID if the pairing exists.
  *               Returns 0 if term ID 0 is passed to the function.
+ *
+ * @phpstan-return (
+ *     $tag_name is 0
+ *         ? 0
+ *         : ($tag_name is '' ? null : array{term_id: string, term_taxonomy_id: string}|null)
+ * )
  */
 function tag_exists( $tag_name ) {
 	return term_exists( $tag_name, 'post_tag' );
diff --git a/src/wp-admin/includes/template.php b/src/wp-admin/includes/template.php
index a24aae32cc8dd..b29b7d481b489 100644
--- a/src/wp-admin/includes/template.php
+++ b/src/wp-admin/includes/template.php
@@ -1302,6 +1302,8 @@ function _get_plugin_from_callback( $callback ) {
  *                                      Often this is the object that's the focus of the current screen,
  *                                      for example a `WP_Post` or `WP_Comment` object.
  * @return int Number of meta_boxes.
+ *
+ * @phpstan-return int<0, max>
  */
 function do_meta_boxes( $screen, $context, $data_object ) {
 	global $wp_meta_boxes;
@@ -1708,6 +1710,8 @@ function add_settings_section( $id, $title, $callback, $page, $args = array() )
  *     @type string $class     CSS Class to be added to the `<tr>` element when the
  *                             field is output.
  * }
+ *
+ * @phpstan-return void
  */
 function add_settings_field( $id, $title, $callback, $page, $section = 'default', $args = array() ) {
 	global $wp_settings_fields;
@@ -2124,6 +2128,8 @@ function _admin_search_query() {
  *
  * @param string $title      Optional. Title of the Iframe page. Default empty.
  * @param bool   $deprecated Not used.
+ *
+ * @phpstan-param false $deprecated
  */
 function iframe_header( $title = '', $deprecated = false ) {
 	global $hook_suffix, $admin_body_class, $body_id, $wp_locale;
@@ -2633,6 +2639,8 @@ function submit_button( $text = '', $type = 'primary', $name = 'submit', $wrap =
  *                                       e.g. `id="search-submit"`, though the array format is generally preferred.
  *                                       Default empty string.
  * @return string Submit button HTML.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_submit_button( $text = '', $type = 'primary large', $name = 'submit', $wrap = true, $other_attributes = '' ) {
 	if ( ! is_array( $type ) ) {
diff --git a/src/wp-admin/includes/update.php b/src/wp-admin/includes/update.php
index b0e998264fe06..bc74d0595453b 100644
--- a/src/wp-admin/includes/update.php
+++ b/src/wp-admin/includes/update.php
@@ -432,6 +432,7 @@ function wp_plugin_update_rows() {
 		$plugins = array_keys( $plugins->response );
 
 		foreach ( $plugins as $plugin_file ) {
+			// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 			add_action( "after_plugin_row_{$plugin_file}", 'wp_plugin_update_row', 10, 2 );
 		}
 	}
@@ -657,6 +658,7 @@ function wp_theme_update_rows() {
 		$themes = array_keys( $themes->response );
 
 		foreach ( $themes as $theme ) {
+			// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 			add_action( "after_theme_row_{$theme}", 'wp_theme_update_row', 10, 2 );
 		}
 	}
diff --git a/src/wp-admin/includes/upgrade.php b/src/wp-admin/includes/upgrade.php
index 244401cf24013..461ab78a219e5 100644
--- a/src/wp-admin/includes/upgrade.php
+++ b/src/wp-admin/includes/upgrade.php
@@ -43,6 +43,8 @@
 	 *     @type string $password         The password of the site owner, if their user account didn't already exist.
 	 *     @type string $password_message The explanatory message regarding the password.
 	 * }
+	 *
+	 * @phpstan-param '' $deprecated
 	 */
 	function wp_install(
 		$blog_title,
@@ -1865,7 +1867,7 @@ function upgrade_340() {
 		if ( 'yes' === $wpdb->get_var( "SELECT autoload FROM $wpdb->options WHERE option_name = 'uninstall_plugins'" ) ) {
 			$uninstall_plugins = get_option( 'uninstall_plugins' );
 			delete_option( 'uninstall_plugins' );
-			add_option( 'uninstall_plugins', $uninstall_plugins, null, false );
+			add_option( 'uninstall_plugins', $uninstall_plugins, '', false );
 		}
 	}
 }
diff --git a/src/wp-admin/includes/widgets.php b/src/wp-admin/includes/widgets.php
index e751602866b0d..5697a6e9ff0dd 100644
--- a/src/wp-admin/includes/widgets.php
+++ b/src/wp-admin/includes/widgets.php
@@ -322,6 +322,8 @@ function wp_widget_control( $sidebar_args ) {
 /**
  * @param string $classes
  * @return string Modified body classes.
+ *
+ * @phpstan-return non-falsy-string
  */
 function wp_widgets_access_body_class( $classes ) {
 	return "$classes widgets_access ";
diff --git a/src/wp-admin/update.php b/src/wp-admin/update.php
index a6c59ec06dab2..a0ba9cfc069b2 100644
--- a/src/wp-admin/update.php
+++ b/src/wp-admin/update.php
@@ -87,7 +87,7 @@
 			wp_redirect( admin_url( 'update.php?action=activate-plugin&success=true&plugin=' . urlencode( $plugin ) . '&_wpnonce=' . $_GET['_wpnonce'] ) );
 			die();
 		}
-		iframe_header( __( 'Plugin Reactivation' ), true );
+		iframe_header( __( 'Plugin Reactivation' ) );
 		if ( isset( $_GET['success'] ) ) {
 			echo '<p>' . __( 'Plugin reactivated successfully.' ) . '</p>';
 		}
diff --git a/src/wp-content/themes/twentytwentyone/inc/template-functions.php b/src/wp-content/themes/twentytwentyone/inc/template-functions.php
index f141b99a8cf8f..6af17e19ff5d6 100644
--- a/src/wp-content/themes/twentytwentyone/inc/template-functions.php
+++ b/src/wp-content/themes/twentytwentyone/inc/template-functions.php
@@ -50,7 +50,7 @@ function twenty_twenty_one_post_classes( $classes ) {
 
 	return $classes;
 }
-add_filter( 'post_class', 'twenty_twenty_one_post_classes', 10, 3 );
+add_filter( 'post_class', 'twenty_twenty_one_post_classes' );
 
 /**
  * Adds a pingback url auto-discovery header for single posts, pages, or attachments.
diff --git a/src/wp-includes/abilities-api.php b/src/wp-includes/abilities-api.php
index 393e40b56ed8c..66dd394809a23 100644
--- a/src/wp-includes/abilities-api.php
+++ b/src/wp-includes/abilities-api.php
@@ -292,6 +292,8 @@
  *                                                     of ability behavior.
  * }
  * @return WP_Ability|null The registered ability instance on success, `null` on failure.
+ *
+ * @phpstan-param lowercase-string&non-falsy-string $name
  */
 function wp_register_ability( string $name, array $args ): ?WP_Ability {
 	if ( ! doing_action( 'wp_abilities_api_init' ) ) {
diff --git a/src/wp-includes/author-template.php b/src/wp-includes/author-template.php
index b27bbf62379d4..014adad971ca5 100644
--- a/src/wp-includes/author-template.php
+++ b/src/wp-includes/author-template.php
@@ -20,6 +20,8 @@
  *
  * @param string $deprecated Deprecated.
  * @return string The author's display name, empty string if unknown.
+ *
+ * @phpstan-param '' $deprecated
  */
 function get_the_author( $deprecated = '' ) {
 	global $authordata;
@@ -57,6 +59,9 @@ function get_the_author( $deprecated = '' ) {
  * @param string $deprecated      Deprecated.
  * @param bool   $deprecated_echo Deprecated. Use get_the_author(). Echo the string or return it.
  * @return string The author's display name, from get_the_author().
+ *
+ * @phpstan-param '' $deprecated
+ * @phpstan-param true $deprecated_echo
  */
 function the_author( $deprecated = '', $deprecated_echo = true ) {
 	if ( ! empty( $deprecated ) ) {
@@ -362,6 +367,8 @@ function get_the_author_posts_link() {
  * @since 4.4.0 Converted into a wrapper for get_the_author_posts_link()
  *
  * @param string $deprecated Unused.
+ *
+ * @phpstan-param '' $deprecated
  */
 function the_author_posts_link( $deprecated = '' ) {
 	if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/block-patterns.php b/src/wp-includes/block-patterns.php
index 50ca1a426378d..3e50b349d242c 100644
--- a/src/wp-includes/block-patterns.php
+++ b/src/wp-includes/block-patterns.php
@@ -277,6 +277,8 @@ function wp_normalize_remote_block_pattern( $pattern ) {
  * @since 6.3.0 Add 'pattern-directory/core' to the pattern's 'source'.
  *
  * @param WP_Screen $deprecated Unused. Formerly the screen that the current request was triggered from.
+ *
+ * @phpstan-param null $deprecated
  */
 function _load_remote_block_patterns( $deprecated = null ) {
 	if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/block-supports/block-style-variations.php b/src/wp-includes/block-supports/block-style-variations.php
index a808ea3d74ecf..6c863056044b1 100644
--- a/src/wp-includes/block-supports/block-style-variations.php
+++ b/src/wp-includes/block-supports/block-style-variations.php
@@ -262,7 +262,7 @@ function wp_enqueue_block_style_variation_styles() {
 // Register the block support.
 WP_Block_Supports::get_instance()->register( 'block-style-variation', array() );
 
-add_filter( 'render_block_data', 'wp_render_block_style_variation_support_styles', 10, 2 );
+add_filter( 'render_block_data', 'wp_render_block_style_variation_support_styles' );
 add_filter( 'render_block', 'wp_render_block_style_variation_class_name', 10, 2 );
 add_action( 'wp_enqueue_scripts', 'wp_enqueue_block_style_variation_styles', 1 );
 
diff --git a/src/wp-includes/block-supports/elements.php b/src/wp-includes/block-supports/elements.php
index d765a2c2b4b5a..b2bcc1dba9ade 100644
--- a/src/wp-includes/block-supports/elements.php
+++ b/src/wp-includes/block-supports/elements.php
@@ -13,6 +13,8 @@
  * @access private
  *
  * @return string The unique class name.
+ *
+ * @phpstan-return lowercase-string&non-falsy-string
  */
 function wp_get_elements_class_name(): string {
 	return wp_unique_prefixed_id( 'wp-elements-' );
diff --git a/src/wp-includes/block-supports/typography.php b/src/wp-includes/block-supports/typography.php
index e99d0254fb43d..dda44c0e5293b 100644
--- a/src/wp-includes/block-supports/typography.php
+++ b/src/wp-includes/block-supports/typography.php
@@ -560,6 +560,8 @@ function wp_get_computed_fluid_typography_value( $args = array() ) {
  * @param bool|array $settings Optional Theme JSON settings array that overrides any global theme settings.
  *                             Default is false.
  * @return string|null Font-size value or null if a size is not passed in $preset.
+ *
+ * @phpstan-param array $settings
  */
 
 
diff --git a/src/wp-includes/block-template-utils.php b/src/wp-includes/block-template-utils.php
index 4dcba75c6d8af..7db660b74cde9 100644
--- a/src/wp-includes/block-template-utils.php
+++ b/src/wp-includes/block-template-utils.php
@@ -1476,6 +1476,8 @@ function wp_is_theme_directory_ignored( $path ) {
  * @since 6.0.0 Adds the whole theme to the export archive.
  *
  * @return WP_Error|string Path of the ZIP file or error on failure.
+ *
+ * @phpstan-return non-falsy-string|WP_Error
  */
 function wp_generate_block_templates_export_file() {
 	$wp_version = wp_get_wp_version();
@@ -1696,6 +1698,8 @@ function get_template_hierarchy( $slug, $is_custom = false, $template_prefix = '
  *                                    prepared for inserting or updating the database.
  * @param WP_REST_Request $deprecated Deprecated. Not used.
  * @return stdClass|WP_Error The updated object representing a template or template part.
+ *
+ * @phpstan-param null $deprecated
  */
 function inject_ignored_hooked_blocks_metadata_attributes( $changes, $deprecated = null ) {
 	if ( null !== $deprecated ) {
diff --git a/src/wp-includes/blocks.php b/src/wp-includes/blocks.php
index 487c2765ac249..95a73e50c77b8 100644
--- a/src/wp-includes/blocks.php
+++ b/src/wp-includes/blocks.php
@@ -2682,6 +2682,8 @@ function _wp_apply_block_content_filters( $content, $context = '', &$seen_ids =
  *
  * @param string $content Content to test.
  * @return int The block format version is 1 if the content contains one or more blocks, 0 otherwise.
+ *
+ * @phpstan-return ($content is '' ? 0 : 0|1)
  */
 function block_version( $content ) {
 	return has_blocks( $content ) ? 1 : 0;
@@ -3082,6 +3084,8 @@ static function ( $format ) {
  * @param WP_Block $block   Block instance.
  * @param bool     $is_next Flag for handling `next/previous` blocks.
  * @return string|null The pagination arrow HTML or null if there is none.
+ *
+ * @phpstan-return non-falsy-string|null
  */
 function get_query_pagination_arrow( $block, $is_next ) {
 	$arrow_map = array(
@@ -3182,6 +3186,8 @@ function build_comment_query_vars_from_block( $block ) {
  * @param string   $pagination_type Optional. Type of the arrow we will be rendering.
  *                                  Accepts 'next' or 'previous'. Default 'next'.
  * @return string|null The pagination arrow HTML or null if there is none.
+ *
+ * @phpstan-return non-falsy-string|null
  */
 function get_comments_pagination_arrow( $block, $pagination_type = 'next' ) {
 	$arrow_map = array(
diff --git a/src/wp-includes/bookmark.php b/src/wp-includes/bookmark.php
index 9e44d781909ed..2aabc22f2429f 100644
--- a/src/wp-includes/bookmark.php
+++ b/src/wp-includes/bookmark.php
@@ -20,6 +20,13 @@
  *                               respectively. Default OBJECT.
  * @param string       $filter   Optional. How to sanitize bookmark fields. Default 'raw'.
  * @return array|object|null Type returned depends on $output value.
+ *
+ * @phpstan-param 'OBJECT'|'ARRAY_A'|'ARRAY_N' $output
+ * @phpstan-return null|(
+ *     $output is 'ARRAY_A'
+ *         ? array<string, mixed>
+ *         : ($output is 'ARRAY_N' ? array<int, mixed> : stdClass)
+ * )
  */
 function get_bookmark( $bookmark, $output = OBJECT, $filter = 'raw' ) {
 	global $wpdb;
@@ -74,6 +81,9 @@ function get_bookmark( $bookmark, $output = OBJECT, $filter = 'raw' ) {
  * @param int    $bookmark The bookmark ID to get field.
  * @param string $context  Optional. The context of how the field will be used. Default 'display'.
  * @return string|WP_Error
+ *
+ * @phpstan-param 'link_id'|'link_url'|'link_name'|'link_image'|'link_target'|'link_description'|'link_visible'|'link_owner'|'link_rating'|'link_updated'|'link_rel'|'link_notes'|'link_rss'|'link_category' $field
+ * @phpstan-return array<int, int<1, max>>|int|string
  */
 function get_bookmark_field( $field, $bookmark, $context = 'display' ) {
 	$bookmark = (int) $bookmark;
@@ -396,6 +406,9 @@ function sanitize_bookmark( $bookmark, $context = 'display' ) {
  * @param string $context     How to filter the field value. Accepts 'raw', 'edit', 'db',
  *                            'display', 'attribute', or 'js'. Default 'display'.
  * @return mixed The filtered value.
+ *
+ * @phpstan-param 'link_id'|'link_url'|'link_name'|'link_image'|'link_target'|'link_description'|'link_visible'|'link_owner'|'link_rating'|'link_updated'|'link_rel'|'link_notes'|'link_rss'|'link_category' $field
+ * @phpstan-return array<int, int>|int|string
  */
 function sanitize_bookmark_field( $field, $value, $bookmark_id, $context ) {
 	$int_fields = array( 'link_id', 'link_rating' );
diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index f268f93cbc461..3f87eff239b2a 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -43,6 +43,8 @@ function get_category_link( $category ) {
  * @param bool   $nicename    Optional. Whether to use nice name for display. Default false.
  * @param array  $deprecated  Not used.
  * @return string|WP_Error A list of category parents on success, WP_Error on failure.
+ *
+ * @phpstan-param array{} $deprecated
  */
 function get_category_parents( $category_id, $link = false, $separator = '/', $nicename = false, $deprecated = array() ) {
 
@@ -534,6 +536,8 @@ function wp_dropdown_categories( $args = '' ) {
  * }
  * @return void|string|false Void if 'echo' argument is true, HTML list of categories if 'echo' is false.
  *                           False if the taxonomy does not exist.
+ *
+ * @phpstan-return ($args is array{echo: false|0, ...} ? string|false : false|void)
  */
 function wp_list_categories( $args = '' ) {
 	$defaults = array(
@@ -849,6 +853,8 @@ function default_topic_count_scale( $count ) {
  *                                                0, 1, or their bool equivalents.
  * }
  * @return string|string[] Tag cloud as a string or an array, depending on 'format' argument.
+ *
+ * @phpstan-return ($args is array{format: 'array', ...} ? array<int, string> : string)
  */
 function wp_generate_tag_cloud( $tags, $args = '' ) {
 	$defaults = array(
diff --git a/src/wp-includes/category.php b/src/wp-includes/category.php
index dbb48d630b076..eb9f83a2ed156 100644
--- a/src/wp-includes/category.php
+++ b/src/wp-includes/category.php
@@ -22,6 +22,24 @@
  *     @type string $taxonomy Taxonomy to retrieve terms for. Default 'category'.
  * }
  * @return array List of category objects.
+ *
+ * @phpstan-return (
+ *     $args is array{fields: 'count', ...}
+ *         ? list<numeric-string>
+ *         : (
+ *             $args is array{fields: 'names'|'slugs', ...}
+ *                 ? list<string>
+ *                 : (
+ *                     $args is array{fields: 'id=>name'|'id=>slug', ...}
+ *                         ? array<int, string>
+ *                         : (
+ *                             $args is array{fields: 'id=>parent', ...}
+ *                                 ? array<int, int>
+ *                                 : ($args is array{fields: 'ids'|'tt_ids', ...} ? list<int> : array<int, WP_Term>)
+ *                         )
+ *                 )
+ *         )
+ * )
  */
 function get_categories( $args = '' ) {
 	$defaults = array( 'taxonomy' => 'category' );
@@ -88,6 +106,9 @@ function get_categories( $args = '' ) {
  * @return WP_Term|array|WP_Error|null Category data in type defined by $output parameter.
  *                                     Returns a WP_Term object with backwards compatible property aliases filled in.
  *                                     WP_Error if $category is empty, null if it does not exist.
+ *
+ * @phpstan-param 'OBJECT'|'ARRAY_A'|'ARRAY_N' $output
+ * @phpstan-return ($category is object ? array<array-key, mixed>|WP_Term : array<array-key, mixed>|WP_Term|WP_Error|null) & ($output is 'ARRAY_A' ? array<string, mixed>|WP_Error|null : ($output is 'ARRAY_N' ? array<int, mixed>|WP_Error|null : WP_Term|WP_Error|null))
  */
 function get_category( $category, $output = OBJECT, $filter = 'raw' ) {
 	$category = get_term( $category, 'category', $output, $filter );
@@ -121,6 +142,13 @@ function get_category( $category, $output = OBJECT, $filter = 'raw' ) {
  *                              correspond to a WP_Term object, an associative array, or a numeric array,
  *                              respectively. Default OBJECT.
  * @return WP_Term|array|WP_Error|null Type is based on $output value.
+ *
+ * @phpstan-param 'OBJECT'|'ARRAY_A'|'ARRAY_N' $output
+ * @phpstan-return (
+ *     $output is 'ARRAY_A'
+ *         ? array<string, mixed>|WP_Error|null
+ *         : ($output is 'ARRAY_N' ? array<int, mixed>|WP_Error|null : WP_Term|WP_Error|null)
+ * )
  */
 function get_category_by_path( $category_path, $full_match = true, $output = OBJECT ) {
 	$category_path  = rawurlencode( urldecode( $category_path ) );
@@ -259,6 +287,10 @@ function cat_is_ancestor_of( $cat1, $cat2 ) {
  * @param object|array $category Category data.
  * @param string       $context  Optional. Default 'display'.
  * @return object|array Same type as $category with sanitized data for safe use.
+ *
+ * @phpstan-template T of array|object
+ * @phpstan-param T $category
+ * @phpstan-return T
  */
 function sanitize_category( $category, $context = 'display' ) {
 	return sanitize_term( $category, 'category', $context );
@@ -293,6 +325,20 @@ function sanitize_category_field( $field, $value, $cat_id, $context ) {
  * }
  * @return WP_Term[]|int|WP_Error Array of 'post_tag' term objects, a count thereof,
  *                                or WP_Error if any of the taxonomies do not exist.
+ *
+ * @phpstan-return (
+ *     $args is array{fields: 'names'|'slugs', ...}
+ *         ? list<string>
+ *         : (
+ *             $args is array{fields: 'id=>name'|'id=>slug', ...}
+ *                 ? array<int, string>
+ *                 : (
+ *                     $args is array{fields: 'id=>parent', ...}
+ *                         ? array<int, int>
+ *                         : ( $args is array{fields: 'ids'|'tt_ids', ...} ? list<int> : array<int, WP_Term> )
+ *                 )
+ *         )
+ * )|WP_Error
  */
 function get_tags( $args = '' ) {
 	$defaults = array( 'taxonomy' => 'post_tag' );
diff --git a/src/wp-includes/class-wp-ajax-response.php b/src/wp-includes/class-wp-ajax-response.php
index ab747618e0fbf..b9946343ac79f 100644
--- a/src/wp-includes/class-wp-ajax-response.php
+++ b/src/wp-includes/class-wp-ajax-response.php
@@ -63,6 +63,8 @@ public function __construct( $args = '' ) {
 	 *                                             element as CDATA. Default empty array.
 	 * }
 	 * @return string XML response.
+	 *
+	 * @phpstan-return non-falsy-string
 	 */
 	public function add( $args = '' ) {
 		$defaults = array(
diff --git a/src/wp-includes/class-wp-block-list.php b/src/wp-includes/class-wp-block-list.php
index b56b3bd69dc3c..fb21ef75a5536 100644
--- a/src/wp-includes/class-wp-block-list.php
+++ b/src/wp-includes/class-wp-block-list.php
@@ -10,6 +10,8 @@
  * Class representing a list of block instances.
  *
  * @since 5.5.0
+ *
+ * @phpstan-implements ArrayAccess<int, WP_Block>
  */
 #[AllowDynamicProperties]
 class WP_Block_List implements Iterator, ArrayAccess, Countable {
@@ -69,6 +71,8 @@ public function __construct( $blocks, $available_context = array(), $registry =
 	 *
 	 * @param int $offset Offset of block to check for.
 	 * @return bool Whether block exists.
+	 *
+	 * @phpstan-param int $offset
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetExists( $offset ) {
@@ -84,6 +88,9 @@ public function offsetExists( $offset ) {
 	 *
 	 * @param int $offset Offset of block value to retrieve.
 	 * @return WP_Block|null Block value if exists, or null.
+	 *
+	 * @phpstan-param int $offset
+	 * @phpstan-return WP_Block|null
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetGet( $offset ) {
@@ -107,6 +114,9 @@ public function offsetGet( $offset ) {
 	 *
 	 * @param int            $offset Offset of block value to set.
 	 * @param array|WP_Block $value  Block value.
+	 *
+	 * @phpstan-param int|null $offset
+	 * @phpstan-return void
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetSet( $offset, $value ) {
@@ -125,6 +135,9 @@ public function offsetSet( $offset, $value ) {
 	 * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
 	 *
 	 * @param int $offset Offset of block value to unset.
+	 *
+	 * @phpstan-param int $offset
+	 * @phpstan-return void
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetUnset( $offset ) {
diff --git a/src/wp-includes/class-wp-block-supports.php b/src/wp-includes/class-wp-block-supports.php
index cf2d84f3b6756..41cbe2b81c41a 100644
--- a/src/wp-includes/class-wp-block-supports.php
+++ b/src/wp-includes/class-wp-block-supports.php
@@ -197,6 +197,9 @@ private function register_attributes() {
  *
  * @param string[] $extra_attributes Optional. Array of extra attributes to render on the block wrapper.
  * @return string String of HTML attributes.
+ *
+ * @phpstan-param array<string, string> $extra_attributes
+ * @phpstan-return ($extra_attributes is empty ? string : non-falsy-string)
  */
 function get_block_wrapper_attributes( $extra_attributes = array() ) {
 	$new_attributes = WP_Block_Supports::get_instance()->apply_block_supports();
diff --git a/src/wp-includes/class-wp-customize-setting.php b/src/wp-includes/class-wp-customize-setting.php
index 68dd8b1433857..e5c9615124da2 100644
--- a/src/wp-includes/class-wp-customize-setting.php
+++ b/src/wp-includes/class-wp-customize-setting.php
@@ -362,6 +362,7 @@ public function preview() {
 		// If the setting does not need previewing now, defer to when it has a value to preview.
 		if ( ! $needs_preview ) {
 			if ( ! has_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) ) ) {
+				// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 				add_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) );
 			}
 			return false;
diff --git a/src/wp-includes/class-wp-dependencies.php b/src/wp-includes/class-wp-dependencies.php
index c2daba389bd75..4791b3f7b3255 100644
--- a/src/wp-includes/class-wp-dependencies.php
+++ b/src/wp-includes/class-wp-dependencies.php
@@ -74,6 +74,8 @@ class WP_Dependencies {
 	 * @since 2.8.0
 	 *
 	 * @var (int|false)[]
+	 *
+	 * @phpstan-var array<string, int|false>
 	 */
 	public $groups = array();
 
@@ -472,6 +474,16 @@ protected function recurse_deps( $queue, $handle ) {
 	 * @param string $handle Name of the item. Should be unique.
 	 * @param string $status Optional. Status of the item to query. Default 'registered'.
 	 * @return bool|_WP_Dependency Found, or object Item data.
+	 *
+	 * @phpstan-return (
+	 *     $handle is not non-empty-string
+	 *         ? false
+	 *         : (
+	 *             $status is not 'registered'|'scripts'|'enqueued'|'queued'|'to_do'|'to_print'|'done'|'printed'
+	 *                 ? false
+	 *                 : ( $status is 'registered'|'scripts' ? _WP_Dependency|false : bool )
+	 *         )
+	 * )
 	 */
 	public function query( $handle, $status = 'registered' ) {
 		switch ( $status ) {
@@ -529,6 +541,8 @@ public function set_group( $handle, $recursion, $group ) {
 	 *
 	 * @param string[] $load Array of script or style handles to load.
 	 * @return string Etag header.
+	 *
+	 * @phpstan-return non-falsy-string
 	 */
 	public function get_etag( $load ) {
 		/*
diff --git a/src/wp-includes/class-wp-http.php b/src/wp-includes/class-wp-http.php
index 13b82d95bfbd2..20d61ebf98cfb 100644
--- a/src/wp-includes/class-wp-http.php
+++ b/src/wp-includes/class-wp-http.php
@@ -633,6 +633,15 @@ private function _dispatch_request( $url, $args ) {
 	 * @param string|array $args Optional. Override the defaults.
 	 * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
 	 *                        A WP_Error instance upon error. See WP_Http::response() for details.
+	 *
+	 * @phpstan-return array{
+	 *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+	 *     body: string,
+	 *     response: array{code: int, message: string},
+	 *     cookies: array<int, WP_Http_Cookie>,
+	 *     filename: string|null,
+	 *     http_response: WP_HTTP_Requests_Response,
+	 * }|WP_Error
 	 */
 	public function post( $url, $args = array() ) {
 		$defaults    = array( 'method' => 'POST' );
@@ -651,6 +660,15 @@ public function post( $url, $args = array() ) {
 	 * @param string|array $args Optional. Override the defaults.
 	 * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
 	 *                        A WP_Error instance upon error. See WP_Http::response() for details.
+	 *
+	 * @phpstan-return array{
+	 *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+	 *     body: string,
+	 *     response: array{code: int, message: string},
+	 *     cookies: array<int, WP_Http_Cookie>,
+	 *     filename: string|null,
+	 *     http_response: WP_HTTP_Requests_Response,
+	 * }|WP_Error
 	 */
 	public function get( $url, $args = array() ) {
 		$defaults    = array( 'method' => 'GET' );
@@ -669,6 +687,15 @@ public function get( $url, $args = array() ) {
 	 * @param string|array $args Optional. Override the defaults.
 	 * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
 	 *                        A WP_Error instance upon error. See WP_Http::response() for details.
+	 *
+	 * @phpstan-return array{
+	 *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+	 *     body: string,
+	 *     response: array{code: int, message: string},
+	 *     cookies: array<int, WP_Http_Cookie>,
+	 *     filename: string|null,
+	 *     http_response: WP_HTTP_Requests_Response,
+	 * }|WP_Error
 	 */
 	public function head( $url, $args = array() ) {
 		$defaults    = array( 'method' => 'HEAD' );
diff --git a/src/wp-includes/class-wp-locale.php b/src/wp-includes/class-wp-locale.php
index e18c0c4f1d897..37a2abf5cec53 100644
--- a/src/wp-includes/class-wp-locale.php
+++ b/src/wp-includes/class-wp-locale.php
@@ -119,6 +119,8 @@ class WP_Locale {
 	 *
 	 * @since 6.2.0
 	 * @var string
+	 *
+	 * @phpstan-var 'characters_excluding_spaces'|'characters_including_spaces'|'words'
 	 */
 	public $word_count_type;
 
@@ -442,6 +444,8 @@ public function get_list_item_separator() {
 	 *
 	 * @return string Localized word count type. Possible values are `characters_excluding_spaces`,
 	 *                `characters_including_spaces`, or `words`. Defaults to `words`.
+	 *
+	 * @phpstan-return 'characters_excluding_spaces'|'characters_including_spaces'|'words'
 	 */
 	public function get_word_count_type() {
 
diff --git a/src/wp-includes/class-wp-object-cache.php b/src/wp-includes/class-wp-object-cache.php
index cda63e66d49ef..d79246ad2e3b0 100644
--- a/src/wp-includes/class-wp-object-cache.php
+++ b/src/wp-includes/class-wp-object-cache.php
@@ -420,6 +420,8 @@ public function get_multiple( $keys, $group = 'default', $force = false ) {
 	 * @param string     $group      Optional. Where the cache contents are grouped. Default 'default'.
 	 * @param bool       $deprecated Optional. Unused. Default false.
 	 * @return bool True on success, false if the contents were not deleted.
+	 *
+	 * @phpstan-param false $deprecated
 	 */
 	public function delete( $key, $group = 'default', $deprecated = false ) {
 		if ( ! $this->is_valid_key( $key ) ) {
diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index 9385ae832ff66..7cf09cd4ca24d 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -14,6 +14,10 @@
  *
  * @since 1.5.0
  * @since 4.5.0 Removed the `$comments_popup` property.
+ *
+ * @phpstan-property-read bool $query_vars_changed
+ * @phpstan-property-read bool|string $query_vars_hash
+ * @phpstan-method void init_query_flags()
  */
 #[AllowDynamicProperties]
 class WP_Query {
diff --git a/src/wp-includes/class-wp-recovery-mode.php b/src/wp-includes/class-wp-recovery-mode.php
index 8fa6bf22cbdea..b1cbf6af8442b 100644
--- a/src/wp-includes/class-wp-recovery-mode.php
+++ b/src/wp-includes/class-wp-recovery-mode.php
@@ -92,6 +92,7 @@ public function __construct() {
 	public function initialize() {
 		$this->is_initialized = true;
 
+		// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 		add_action( 'wp_logout', array( $this, 'exit_recovery_mode' ) );
 		add_action( 'login_form_' . self::EXIT_ACTION, array( $this, 'handle_exit_recovery_mode' ) );
 		add_action( 'recovery_mode_clean_expired_keys', array( $this, 'clean_expired_keys' ) );
diff --git a/src/wp-includes/class-wp-theme-json-resolver.php b/src/wp-includes/class-wp-theme-json-resolver.php
index b6c205bba03bd..da7720d9e89d8 100644
--- a/src/wp-includes/class-wp-theme-json-resolver.php
+++ b/src/wp-includes/class-wp-theme-json-resolver.php
@@ -240,6 +240,8 @@ protected static function has_same_registered_blocks( $origin ) {
 	 *     @type bool $with_supports Whether to include theme supports in the data. Default true.
 	 * }
 	 * @return WP_Theme_JSON Entity that holds theme data.
+	 *
+	 * @phpstan-param array{} $deprecated
 	 */
 	public static function get_theme_data( $deprecated = array(), $options = array() ) {
 		if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/class-wp-theme.php b/src/wp-includes/class-wp-theme.php
index 87399e399a198..2dfd6188f5ed3 100644
--- a/src/wp-includes/class-wp-theme.php
+++ b/src/wp-includes/class-wp-theme.php
@@ -5,6 +5,22 @@
  * @package WordPress
  * @subpackage Theme
  * @since 3.4.0
+ *
+ * @phpstan-type ThemeKey 'Name'|'Version'|'Status'|'Title'|'Author'|'Author Name'|'Author URI'|'Description'|'Template'|'Stylesheet'|'Template Files'|'Stylesheet Files'|'Template Dir'|'Stylesheet Dir'|'Screenshot'|'Tags'|'Theme Root'|'Theme Root URI'|'Parent Theme'
+ * @phpstan-property-read string $name
+ * @phpstan-property-read string $title
+ * @phpstan-property-read string $version
+ * @phpstan-property-read string $parent_theme
+ * @phpstan-property-read string $template_dir
+ * @phpstan-property-read string $stylesheet_dir
+ * @phpstan-property-read string $template
+ * @phpstan-property-read string $stylesheet
+ * @phpstan-property-read string $screenshot
+ * @phpstan-property-read string $description
+ * @phpstan-property-read string $author
+ * @phpstan-property-read list<string> $tags
+ * @phpstan-property-read string $theme_root
+ * @phpstan-property-read string $theme_root_uri
  */
 #[AllowDynamicProperties]
 final class WP_Theme implements ArrayAccess {
@@ -654,6 +670,8 @@ public function offsetUnset( $offset ) {}
 	 *
 	 * @param mixed $offset
 	 * @return bool
+	 *
+	 * @phpstan-return ($offset is ThemeKey ? true : false)
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetExists( $offset ) {
@@ -696,6 +714,8 @@ public function offsetExists( $offset ) {
 	 *
 	 * @param mixed $offset
 	 * @return mixed
+	 *
+	 * @phpstan-return ($offset is ThemeKey ? mixed : null)
 	 */
 	#[ReturnTypeWillChange]
 	public function offsetGet( $offset ) {
diff --git a/src/wp-includes/class-wp-widget-factory.php b/src/wp-includes/class-wp-widget-factory.php
index 1f6ed3a58919e..24d3e05de0550 100644
--- a/src/wp-includes/class-wp-widget-factory.php
+++ b/src/wp-includes/class-wp-widget-factory.php
@@ -35,6 +35,7 @@ class WP_Widget_Factory {
 	 * @since 2.8.0
 	 * @var array<string, WP_Widget>
 	 * @phpstan-var array<non-decimal-int-string, WP_Widget>
+	 * @phpstan-var array<int, WP_Widget>
 	 */
 	public $widgets = array();
 
@@ -69,11 +70,14 @@ public function WP_Widget_Factory() {
 	 * @since 7.1.1 The key for an instance is prefixed so that it is never cast to an integer.
 	 *
 	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
+	 *
+	 * @phpstan-param class-string<WP_Widget>|WP_Widget $widget
 	 */
 	public function register( $widget ) {
 		if ( $widget instanceof WP_Widget ) {
 			$this->widgets[ self::INSTANCE_KEY_PREFIX . spl_object_id( $widget ) ] = $widget;
 		} else {
+			// @phpstan-ignore arguments.count (Widget classes declare their own constructor, which takes no arguments.)
 			$this->widgets[ $widget ] = new $widget();
 		}
 	}
@@ -87,6 +91,8 @@ public function register( $widget ) {
 	 * @since 7.1.1 The key for an instance is prefixed so that it is never cast to an integer.
 	 *
 	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
+	 *
+	 * @phpstan-param class-string<WP_Widget>|WP_Widget $widget
 	 */
 	public function unregister( $widget ) {
 		if ( $widget instanceof WP_Widget ) {
diff --git a/src/wp-includes/class-wp-widget.php b/src/wp-includes/class-wp-widget.php
index b131c50db3226..9ae4f908af073 100644
--- a/src/wp-includes/class-wp-widget.php
+++ b/src/wp-includes/class-wp-widget.php
@@ -16,6 +16,8 @@
  *
  * @since 2.8.0
  * @since 4.4.0 Moved to its own file from wp-includes/widgets.php
+ *
+ * @phpstan-template T of array = array<string, mixed>
  */
 #[AllowDynamicProperties]
 class WP_Widget {
@@ -109,6 +111,23 @@ class WP_Widget {
 	 * @param array $args     Display arguments including 'before_title', 'after_title',
 	 *                        'before_widget', and 'after_widget'.
 	 * @param array $instance The settings for the particular instance of the widget.
+	 *
+	 * @phpstan-param T $instance
+	 * @phpstan-param array{
+	 *     name: string,
+	 *     id: string,
+	 *     description: string,
+	 *     class: string,
+	 *     before_widget: string,
+	 *     after_widget: string,
+	 *     before_title: string,
+	 *     after_title: string,
+	 *     before_sidebar: string,
+	 *     after_sidebar: string,
+	 *     show_in_rest: boolean,
+	 *     widget_id: string,
+	 *     widget_name: string,
+	 * } $args
 	 */
 	public function widget( $args, $instance ) {
 		die( 'function WP_Widget::widget() must be overridden in a subclass.' );
@@ -127,6 +146,9 @@ public function widget( $args, $instance ) {
 	 *                            WP_Widget::form().
 	 * @param array $old_instance Old settings for this instance.
 	 * @return array Settings to save or bool false to cancel saving.
+	 *
+	 * @phpstan-param T $new_instance
+	 * @phpstan-param T $old_instance
 	 */
 	public function update( $new_instance, $old_instance ) {
 		return $new_instance;
@@ -140,6 +162,8 @@ public function update( $new_instance, $old_instance ) {
 	 * @param array $instance The settings for the particular instance of the widget.
 	 * @return string|void Default return is 'noform'. A subclass which echoes its own
 	 *                     form returns nothing.
+	 *
+	 * @phpstan-param T $instance
 	 */
 	public function form( $instance ) {
 		echo '<p class="no-options-widget">' . __( 'There are no options for this widget.' ) . '</p>';
@@ -213,6 +237,8 @@ public function WP_Widget( $id_base, $name, $widget_options = array(), $control_
 	 *
 	 * @param string $field_name Field name.
 	 * @return string Name attribute for `$field_name`.
+	 *
+	 * @phpstan-return non-falsy-string
 	 */
 	public function get_field_name( $field_name ) {
 		$pos = strpos( $field_name, '[' );
@@ -238,6 +264,8 @@ public function get_field_name( $field_name ) {
 	 *
 	 * @param string $field_name Field name.
 	 * @return string ID attribute for `$field_name`.
+	 *
+	 * @phpstan-return non-falsy-string
 	 */
 	public function get_field_id( $field_name ) {
 		$field_name = str_replace( array( '[]', '[', ']' ), array( '', '-', '' ), $field_name );
@@ -357,6 +385,8 @@ public function is_preview() {
 	 *
 	 *     @type int $number Number increment used for multiples of the same widget.
 	 * }
+	 *
+	 * @final
 	 */
 	public function display_callback( $args, $widget_args = 1 ) {
 		if ( is_numeric( $widget_args ) ) {
@@ -408,6 +438,9 @@ public function display_callback( $args, $widget_args = 1 ) {
 	 * @global array $wp_registered_widgets
 	 *
 	 * @param int $deprecated Not used.
+	 *
+	 * @phpstan-param 1 $deprecated
+	 * @final
 	 */
 	public function update_callback( $deprecated = 1 ) {
 		global $wp_registered_widgets;
@@ -500,6 +533,8 @@ public function update_callback( $deprecated = 1 ) {
 	 *     @type int $number Number increment used for multiples of the same widget.
 	 * }
 	 * @return string|null
+	 *
+	 * @final
 	 */
 	public function form_callback( $widget_args = 1 ) {
 		if ( is_numeric( $widget_args ) ) {
diff --git a/src/wp-includes/class-wpdb.php b/src/wp-includes/class-wpdb.php
index 5cf9508f8fbdf..f1d4c5bf6beab 100644
--- a/src/wp-includes/class-wpdb.php
+++ b/src/wp-includes/class-wpdb.php
@@ -1454,6 +1454,8 @@ private function _escape_identifier_value( $identifier ) {
 	 * @param mixed       ...$args Further variables to substitute into the query's placeholders
 	 *                             if being called with individual arguments.
 	 * @return string|null Sanitized query string, if there is a query to prepare.
+	 *
+	 * @phpstan-param literal-string $query
 	 */
 	public function prepare( $query, ...$args ) {
 		if ( is_null( $query ) ) {
@@ -3087,6 +3089,8 @@ public function get_var( $query = null, $x = 0, $y = 0 ) {
 	 *         )
 	 *         : null
 	 * )
+	 *
+	 * @phpstan-param int<0, max> $y
 	 */
 	public function get_row( $query = null, $output = OBJECT, $y = 0 ) {
 		$this->func_call = "\$db->get_row(\"$query\",$output,$y)";
diff --git a/src/wp-includes/comment-template.php b/src/wp-includes/comment-template.php
index f7068362174e2..cc2608d4220e1 100644
--- a/src/wp-includes/comment-template.php
+++ b/src/wp-includes/comment-template.php
@@ -893,6 +893,9 @@ function get_comments_link( $post = 0 ) {
  *
  * @param string $deprecated   Not Used.
  * @param string $deprecated_2 Not Used.
+ *
+ * @phpstan-param '' $deprecated
+ * @phpstan-param '' $deprecated_2
  */
 function comments_link( $deprecated = '', $deprecated_2 = '' ) {
 	if ( ! empty( $deprecated ) ) {
@@ -1279,6 +1282,8 @@ function trackback_url( $deprecated_echo = true ) {
  * @since 0.71
  *
  * @param int|string $deprecated Not used (Was $timezone = 0).
+ *
+ * @phpstan-param '' $deprecated
  */
 function trackback_rdf( $deprecated = '' ) {
 	if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/comment.php b/src/wp-includes/comment.php
index 817ad17fa97e3..de738f08a4078 100644
--- a/src/wp-includes/comment.php
+++ b/src/wp-includes/comment.php
@@ -773,7 +773,7 @@ function wp_allow_comment( $commentdata, $wp_error = false ) {
 		wp_unslash( $commentdata['comment_content'] )
 	);
 
-	$dupe_id = $wpdb->get_var( $dupe );
+	$dupe_id = (int) $wpdb->get_var( $dupe );
 
 	/**
 	 * Filters the ID, if any, of the duplicate comment found when creating a new comment.
@@ -1884,6 +1884,8 @@ function wp_unspam_comment( $comment_id ) {
  *
  * @param int|WP_Comment $comment_id Comment ID or WP_Comment object
  * @return string|false Status might be 'trash', 'approved', 'unapproved', 'spam'. False on failure.
+ *
+ * @phpstan-return 'approved'|'spam'|'trash'|'unapproved'|false
  */
 function wp_get_comment_status( $comment_id ) {
 	$comment = get_comment( $comment_id );
@@ -2791,6 +2793,8 @@ function wp_send_note_notification( WP_User $user, WP_Comment $comment, ?WP_Post
  * @param string         $comment_status New comment status, either 'hold', 'approve', 'spam', or 'trash'.
  * @param bool           $wp_error       Whether to return a WP_Error object if there is a failure. Default false.
  * @return bool|WP_Error True on success, false or WP_Error on failure.
+ *
+ * @phpstan-return ($wp_error is false ? bool : true|WP_Error)
  */
 function wp_set_comment_status( $comment_id, $comment_status, $wp_error = false ) {
 	global $wpdb;
@@ -2803,6 +2807,7 @@ function wp_set_comment_status( $comment_id, $comment_status, $wp_error = false
 		case 'approve':
 		case '1':
 			$status = '1';
+			// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 			add_action( 'wp_set_comment_status', 'wp_new_comment_notify_postauthor' );
 			break;
 		case 'spam':
@@ -2865,6 +2870,8 @@ function wp_set_comment_status( $comment_id, $comment_status, $wp_error = false
  * @param bool  $wp_error   Optional. Whether to return a WP_Error on failure. Default false.
  * @return int|false|WP_Error The value 1 if the comment was updated, 0 if not updated.
  *                            False or a WP_Error object on failure.
+ *
+ * @phpstan-return ( $wp_error is false ? int|false : int|WP_Error )
  */
 function wp_update_comment( $commentarr, $wp_error = false ) {
 	global $wpdb;
@@ -3180,6 +3187,8 @@ function wp_update_comment_count_now( $post_id ) {
  * @param string $url        URL to ping.
  * @param string $deprecated Not Used.
  * @return string|false String containing URI on success, false on failure.
+ *
+ * @phpstan-param '' $deprecated
  */
 function discover_pingback_server_uri( $url, $deprecated = '' ) {
 	if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/cron.php b/src/wp-includes/cron.php
index 82889d7cc7e2f..232a25835a543 100644
--- a/src/wp-includes/cron.php
+++ b/src/wp-includes/cron.php
@@ -44,6 +44,9 @@
  *                           database performance issues.
  * @param bool   $wp_error   Optional. Whether to return a WP_Error on failure. Default false.
  * @return bool|WP_Error True if event successfully scheduled. False or WP_Error on failure.
+ *
+ * @phpstan-param list<mixed> $args
+ * @phpstan-return ($wp_error is false ? bool : true|WP_Error)
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array(), $wp_error = false ) {
 	// Make sure timestamp is a positive integer.
@@ -248,6 +251,9 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array(), $wp_error
  *                           database performance issues.
  * @param bool   $wp_error   Optional. Whether to return a WP_Error on failure. Default false.
  * @return bool|WP_Error True if event successfully scheduled. False or WP_Error on failure.
+ *
+ * @phpstan-param list<mixed> $args
+ * @phpstan-return ($wp_error is false ? bool : true|WP_Error)
  */
 function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array(), $wp_error = false ) {
 	// Make sure timestamp is a positive integer.
@@ -363,6 +369,9 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array(), $wp
  *                           database performance issues.
  * @param bool   $wp_error   Optional. Whether to return a WP_Error on failure. Default false.
  * @return bool|WP_Error True if event successfully rescheduled. False or WP_Error on failure.
+ *
+ * @phpstan-param list<mixed> $args
+ * @phpstan-return ($wp_error is false ? bool : true|WP_Error)
  */
 function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array(), $wp_error = false ) {
 	// Make sure timestamp is a positive integer.
@@ -485,6 +494,9 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array(), $
  *                          arguments do not match exactly, the event will not be found. Default empty array.
  * @param bool   $wp_error  Optional. Whether to return a WP_Error on failure. Default false.
  * @return bool|WP_Error True if event successfully unscheduled. False or WP_Error on failure.
+ *
+ * @phpstan-param list<mixed> $args
+ * @phpstan-return ($wp_error is false ? bool : true|WP_Error)
  */
 function wp_unschedule_event( $timestamp, $hook, $args = array(), $wp_error = false ) {
 	// Make sure timestamp is a positive integer.
@@ -572,6 +584,9 @@ function wp_unschedule_event( $timestamp, $hook, $args = array(), $wp_error = fa
  * @return int|false|WP_Error On success an integer indicating number of events unscheduled (0 indicates no
  *                            events were registered with the hook and arguments combination), false or WP_Error
  *                            if unscheduling one or more events fail.
+ *
+ * @phpstan-param list<mixed> $args
+ * @phpstan-return (int<0, max>|($wp_error is false ? false : WP_Error))
  */
 function wp_clear_scheduled_hook( $hook, $args = array(), $wp_error = false ) {
 	/*
@@ -677,6 +692,8 @@ function wp_clear_scheduled_hook( $hook, $args = array(), $wp_error = false ) {
  * @param bool   $wp_error Optional. Whether to return a WP_Error on failure. Default false.
  * @return int|false|WP_Error On success an integer indicating number of events unscheduled (0 indicates no
  *                            events were registered on the hook), false or WP_Error if unscheduling fails.
+ *
+ * @phpstan-return ($wp_error is false ? int<0, max>|false : int<0, max>|WP_Error)
  */
 function wp_unschedule_hook( $hook, $wp_error = false ) {
 	/**
@@ -774,6 +791,8 @@ function wp_unschedule_hook( $hook, $wp_error = false ) {
  *     @type array        $args      Array containing each separate argument to pass to the hook's callback function.
  *     @type int          $interval  Optional. The interval time in seconds for the schedule. Only present for recurring events.
  * }
+ *
+ * @phpstan-param list<mixed> $args
  */
 function wp_get_scheduled_event( $hook, $args = array(), $timestamp = null ) {
 	/**
@@ -855,6 +874,8 @@ function wp_get_scheduled_event( $hook, $args = array(), $timestamp = null ) {
  *                     event, so they must match those used when originally scheduling the event. If the
  *                     arguments do not match exactly, the event will not be found. Default empty array.
  * @return int|false The Unix timestamp (UTC) of the next time the event will occur. False if the event doesn't exist.
+ *
+ * @phpstan-param list<mixed> $args
  */
 function wp_next_scheduled( $hook, $args = array() ) {
 	$next_event = wp_get_scheduled_event( $hook, $args );
@@ -1022,11 +1043,13 @@ function wp_cron(): void {
 		if ( did_action( 'wp_loaded' ) ) {
 			_wp_cron();
 		} else {
+			// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 			add_action( 'wp_loaded', '_wp_cron', 20 );
 		}
 	} elseif ( doing_action( 'shutdown' ) ) {
 		_wp_cron();
 	} else {
+		// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 		add_action( 'shutdown', '_wp_cron' );
 	}
 }
@@ -1181,6 +1204,8 @@ function wp_get_schedules() {
  * @param array  $args Optional. Arguments passed to the event's callback function.
  *                     Default empty array.
  * @return string|false Schedule name on success, false if no schedule.
+ *
+ * @phpstan-param list<mixed> $args
  */
 function wp_get_schedule( $hook, $args = array() ) {
 	$schedule = false;
diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index d16979c9c8fb5..47cc3978dd149 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -118,6 +118,7 @@
 add_action( 'admin_init', 'wp_schedule_update_user_counts' );
 add_action( 'wp_update_user_counts', 'wp_schedule_update_user_counts', 10, 0 );
 foreach ( array( 'user_register', 'deleted_user' ) as $action ) {
+	// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 	add_action( $action, 'wp_maybe_update_user_counts', 10, 0 );
 }
 
@@ -307,7 +308,7 @@
 add_filter( 'pre_kses', 'wp_pre_kses_less_than' );
 add_filter( 'pre_kses', 'wp_pre_kses_block_attributes', 10, 3 );
 add_filter( 'sanitize_title', 'sanitize_title_with_dashes', 10, 3 );
-add_action( 'check_comment_flood', 'check_comment_flood_db', 10, 4 );
+add_action( 'check_comment_flood', 'check_comment_flood_db' );
 add_filter( 'comment_flood_filter', 'wp_throttle_comment_flood', 10, 3 );
 add_filter( 'pre_comment_content', 'wp_rel_ugc', 15 );
 
@@ -357,7 +358,9 @@
 add_action( 'publish_future_post', 'check_and_publish_future_post', 10, 1 );
 add_action( 'wp_head', 'wp_robots', 1 );
 add_action( 'wp_head', 'print_emoji_detection_script', 7 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_head', 'wp_print_styles', 8 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_head', 'wp_print_head_scripts', 9 );
 add_action( 'wp_head', 'wp_generator' );
 add_action( 'wp_head', 'rel_canonical' );
@@ -391,7 +394,9 @@
 // Login actions.
 add_action( 'login_head', 'wp_robots', 1 );
 add_action( 'login_head', 'wp_resource_hints', 8 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'login_head', 'wp_print_head_scripts', 9 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'login_head', 'print_admin_styles', 9 );
 add_action( 'login_head', 'wp_site_icon', 99 );
 add_action( 'login_footer', 'wp_print_footer_scripts', 20 );
@@ -425,6 +430,7 @@
 add_action( 'do_all_pings', 'do_all_pingbacks', 10, 0 );
 add_action( 'do_all_pings', 'do_all_enclosures', 10, 0 );
 add_action( 'do_all_pings', 'do_all_trackbacks', 10, 0 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'do_all_pings', 'generic_ping', 10, 0 );
 
 // Disable pings (pingbacks, trackbacks, and ping service notifications) in non-production environments.
@@ -434,6 +440,7 @@
 
 add_action( 'do_robots', 'do_robots' );
 add_action( 'do_favicon', 'do_favicon' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_before_include_template', 'wp_start_template_enhancement_output_buffer', 1000 ); // Late priority to let `wp_template_enhancement_output_buffer` filters and `wp_finalized_template_enhancement_output_buffer` actions be registered.
 add_action( 'set_comment_cookies', 'wp_set_comment_cookies', 10, 3 );
 add_action( 'sanitize_comment_cookies', 'sanitize_comment_cookies' );
@@ -443,6 +450,7 @@
 add_action( 'shutdown', 'wp_ob_end_flush_all', 1 );
 // Create a revision whenever a post is updated.
 add_action( 'wp_after_insert_post', 'wp_save_post_revision_on_insert', 9, 3 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'post_updated', 'wp_save_post_revision', 10, 1 );
 add_action( 'publish_post', '_publish_post_hook', 5, 1 );
 add_action( 'transition_post_status', '_transition_post_status', 5, 3 );
@@ -464,7 +472,9 @@
 // Cron tasks.
 add_action( 'wp_scheduled_delete', 'wp_scheduled_delete' );
 add_action( 'wp_scheduled_auto_draft_delete', 'wp_delete_auto_drafts' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'importer_scheduled_cleanup', 'wp_delete_attachment' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'upgrader_scheduled_cleanup', 'wp_delete_attachment' );
 add_action( 'delete_expired_transients', 'delete_expired_transients' );
 
@@ -533,7 +543,9 @@
 add_action( 'wp_update_comment_type_batch', '_wp_batch_update_comment_type' );
 
 // Email notifications.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'comment_post', 'wp_new_comment_notify_moderator' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'comment_post', 'wp_new_comment_notify_postauthor' );
 add_action( 'rest_insert_comment', 'wp_new_comment_via_rest_notify_postauthor' );
 add_action( 'rest_insert_comment', 'wp_notify_note_mentions', 10, 3 );
@@ -557,6 +569,7 @@
 add_action( 'init', '_wp_connectors_init', 15 );
 
 // Sitemaps actions.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'init', 'wp_sitemaps_get_server' );
 
 /**
@@ -685,6 +698,7 @@
 add_action( 'change_locale', 'create_initial_taxonomies' );
 
 // Canonical.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'template_redirect', 'redirect_canonical' );
 add_action( 'template_redirect', 'wp_redirect_admin_locations', 1000 );
 
@@ -713,12 +727,16 @@
 
 // Admin Bar.
 // Don't remove. Wrong way to disable.
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'template_redirect', '_wp_admin_bar_init', 0 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'admin_init', '_wp_admin_bar_init' );
 add_action( 'wp_enqueue_scripts', 'wp_enqueue_admin_bar_bump_styles' );
 add_action( 'wp_enqueue_scripts', 'wp_enqueue_admin_bar_header_styles' );
 add_action( 'admin_enqueue_scripts', 'wp_enqueue_admin_bar_header_styles' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'before_signup_header', '_wp_admin_bar_init' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'activate_header', '_wp_admin_bar_init' );
 add_action( 'wp_body_open', 'wp_admin_bar_render', 0 );
 add_action( 'wp_footer', 'wp_admin_bar_render', 1000 ); // Back-compat for themes not using `wp_body_open`.
@@ -742,7 +760,9 @@
 add_action( 'embed_head', 'print_emoji_detection_script' );
 add_action( 'embed_head', 'wp_enqueue_embed_styles', 9 );
 add_action( 'embed_head', 'print_embed_styles' ); // Retained for backwards-compatibility. Unhooked by wp_enqueue_embed_styles().
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'embed_head', 'wp_print_head_scripts', 20 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'embed_head', 'wp_print_styles', 20 );
 add_action( 'embed_head', 'wp_robots' );
 add_action( 'embed_head', 'rel_canonical' );
diff --git a/src/wp-includes/deprecated.php b/src/wp-includes/deprecated.php
index 3b78d1610fdad..3180ef2d21e46 100644
--- a/src/wp-includes/deprecated.php
+++ b/src/wp-includes/deprecated.php
@@ -2518,6 +2518,16 @@ function is_taxonomy( $taxonomy ) {
  * @param string $taxonomy The taxonomy name to use
  * @param int $parent ID of parent term under which to confine the exists search.
  * @return mixed Get the term ID or term object, if exists.
+ *
+ * @phpstan-return (
+ *     $term is 0
+ *         ? 0
+ *         : (
+ *             $term is ''
+ *                 ? null
+ *                 : ($taxonomy is '' ? string|null : array{term_id: string, term_taxonomy_id: string}|null)
+ *         )
+ * )
  */
 function is_term( $term, $taxonomy = '', $parent = 0 ) {
 	_deprecated_function( __FUNCTION__, '3.0.0', 'term_exists()' );
@@ -6498,6 +6508,9 @@ function wp_print_auto_sizes_contain_css_fix() {
  *
  * @param string|array $gpc String or array of data to slash.
  * @return string|array Slashed `$gpc`.
+ *
+ * @phpstan-pure
+ * @phpstan-return ($gpc is string ? string : array)
  */
 function addslashes_gpc( $gpc ) {
 	_deprecated_function( __FUNCTION__, '7.0.0', 'wp_slash()' );
diff --git a/src/wp-includes/embed.php b/src/wp-includes/embed.php
index e87cf4ec57989..6a7501027a978 100644
--- a/src/wp-includes/embed.php
+++ b/src/wp-includes/embed.php
@@ -676,7 +676,7 @@ function get_oembed_response_data_for_url( $url, $args ) {
 		}
 
 		if ( $site && get_current_blog_id() !== (int) $site->blog_id ) {
-			switch_to_blog( $site->blog_id );
+			switch_to_blog( (int) $site->blog_id );
 			$switched_blog = true;
 		}
 	}
diff --git a/src/wp-includes/feed.php b/src/wp-includes/feed.php
index 453cc9063cf75..c282da6b60344 100644
--- a/src/wp-includes/feed.php
+++ b/src/wp-includes/feed.php
@@ -99,6 +99,8 @@ function get_default_feed() {
  *
  * @param string $deprecated Unused.
  * @return string The document title.
+ *
+ * @phpstan-param '&#8211;' $deprecated
  */
 function get_wp_title_rss( $deprecated = '&#8211;' ) {
 	if ( '&#8211;' !== $deprecated ) {
@@ -125,6 +127,8 @@ function get_wp_title_rss( $deprecated = '&#8211;' ) {
  * @since 4.4.0 The optional `$sep` parameter was deprecated and renamed to `$deprecated`.
  *
  * @param string $deprecated Unused.
+ *
+ * @phpstan-param '&#8211;' $deprecated
  */
 function wp_title_rss( $deprecated = '&#8211;' ) {
 	if ( '&#8211;' !== $deprecated ) {
@@ -584,6 +588,8 @@ function atom_enclosure() {
  *
  * @param string $data Input string.
  * @return array array(type, value)
+ *
+ * @phpstan-return array{'html'|'text'|'xhtml', string}
  */
 function prep_atom_text_construct( $data ) {
 	if ( ! str_contains( $data, '<' ) && ! str_contains( $data, '&' ) ) {
diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index b9d551d59d51b..d90ce799e1946 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -611,6 +611,8 @@ function wpautop( $text, $br = true ) {
  *
  * @param string $input The text which has to be formatted.
  * @return string[] Array of the formatted text.
+ *
+ * @phpstan-return non-empty-list<string>
  */
 function wp_html_split( $input ) {
 	return preg_split( get_html_split_regex(), $input, -1, PREG_SPLIT_DELIM_CAPTURE );
@@ -622,6 +624,8 @@ function wp_html_split( $input ) {
  * @since 4.4.0
  *
  * @return string The regular expression.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_html_split_regex() {
 	static $regex;
@@ -2278,6 +2282,9 @@ function sanitize_title_for_query( $title ) {
  *                          When set to 'save', additional entities are converted to hyphens
  *                          or stripped entirely. Default 'display'.
  * @return string The sanitized title.
+ *
+ * @phpstan-param 'display'|'save' $context
+ * @phpstan-return lowercase-string
  */
 function sanitize_title_with_dashes( $title, $raw_title = '', $context = 'display' ) {
 	$title = strip_tags( $title );
@@ -2412,6 +2419,10 @@ function sanitize_title_with_dashes( $title, $raw_title = '', $context = 'displa
  *
  * @param string $orderby Order by clause to be validated.
  * @return string|false Returns $orderby if valid, false otherwise.
+ *
+ * @phpstan-template T of string
+ * @phpstan-param T $orderby
+ * @phpstan-return (T is non-falsy-string ? T|false : false)
  */
 function sanitize_sql_orderby( $orderby ) {
 	if ( preg_match( '/^\s*(([a-z0-9_]+|`[a-z0-9_]+`)(\s+(ASC|DESC))?\s*(,\s*(?=[a-z0-9_`])|$))+$/i', $orderby ) || preg_match( '/^\s*RAND\(\s*\)\s*$/i', $orderby ) ) {
@@ -2488,6 +2499,8 @@ function sanitize_locale_name( $locale_name ) {
  * @param string $content    String of characters to be converted.
  * @param string $deprecated Not used.
  * @return string Converted string.
+ *
+ * @phpstan-param '' $deprecated
  */
 function convert_chars( $content, $deprecated = '' ) {
 	if ( ! empty( $deprecated ) ) {
@@ -2788,6 +2801,17 @@ function format_to_edit( $content, $rich_text = false ) {
  * @param int $number     Number to append zeros to if not greater than threshold.
  * @param int $threshold  Digit places number needs to be to not have zeros added.
  * @return string Adds leading zeros to number if needed.
+ *
+ * @phpstan-param int<0, max> $threshold
+ * @phpstan-return (
+ *     $threshold is 0
+ *         ? lowercase-string&non-empty-string&numeric-string
+ *         : (
+ *             $number is int<0, max>
+ *                 ? lowercase-string&non-empty-string&numeric-string
+ *                 : lowercase-string&non-empty-string
+ *         )
+ * )
  */
 function zeroise( $number, $threshold ) {
 	return sprintf( '%0' . $threshold . 's', $number );
@@ -2800,6 +2824,8 @@ function zeroise( $number, $threshold ) {
  *
  * @param string $value Value to which backslashes will be added.
  * @return string String with backslashes inserted.
+ *
+ * @phpstan-pure
  */
 function backslashit( $value ) {
 	if ( isset( $value[0] ) && $value[0] >= '0' && $value[0] <= '9' ) {
@@ -2821,6 +2847,9 @@ function backslashit( $value ) {
  *
  * @param string $value Value to which trailing slash will be added.
  * @return string String with trailing slash added.
+ *
+ * @phpstan-pure
+ * @phpstan-return non-falsy-string
  */
 function trailingslashit( $value ) {
 	return untrailingslashit( $value ) . '/';
@@ -2836,6 +2865,8 @@ function trailingslashit( $value ) {
  *
  * @param string $value Value from which trailing slashes will be removed.
  * @return string String without the trailing slashes.
+ *
+ * @phpstan-pure
  */
 function untrailingslashit( $value ) {
 	return rtrim( $value, '/\\' );
@@ -2884,6 +2915,10 @@ function stripslashes_from_strings_only( $value ) {
  *
  * @param mixed $value The array or string to be encoded.
  * @return mixed The encoded value.
+ *
+ * @phpstan-template T
+ * @phpstan-param T $value
+ * @phpstan-return T
  */
 function urlencode_deep( $value ) {
 	return map_deep( $value, 'urlencode' );
@@ -2896,6 +2931,10 @@ function urlencode_deep( $value ) {
  *
  * @param mixed $value The array or string to be encoded.
  * @return mixed The encoded value.
+ *
+ * @phpstan-template T
+ * @phpstan-param T $value
+ * @phpstan-return T
  */
 function rawurlencode_deep( $value ) {
 	return map_deep( $value, 'rawurlencode' );
@@ -2908,6 +2947,10 @@ function rawurlencode_deep( $value ) {
  *
  * @param mixed $value The array or string to be decoded.
  * @return mixed The decoded value.
+ *
+ * @phpstan-template T
+ * @phpstan-param T $value
+ * @phpstan-return T
  */
 function urldecode_deep( $value ) {
 	return map_deep( $value, 'urldecode' );
@@ -2948,6 +2991,8 @@ function urldecode_deep( $value ) {
  * @param string $email_address Email address.
  * @param int    $hex_encoding  Optional. Set to 1 to enable hex encoding.
  * @return string Converted email address.
+ *
+ * @phpstan-param 0|1 $hex_encoding
  */
 function antispambot( $email_address, $hex_encoding = 0 ) {
 	$obfuscated     = '';
@@ -3609,6 +3654,8 @@ function convert_smilies( $text ) {
  * @param string $email      Email address to verify.
  * @param bool   $deprecated Deprecated.
  * @return string|false Valid email address on success, false on failure.
+ *
+ * @phpstan-param false $deprecated
  */
 function is_email( $email, $deprecated = false ) {
 	if ( ! empty( $deprecated ) ) {
@@ -5866,6 +5913,8 @@ function sanitize_trackback_urls( $to_ping ) {
  *         T is array ? array<key-of<T>, ( value-of<T> is string ? string : value-of<T> )> : T
  *     )
  * )
+ *
+ * @phpstan-pure
  */
 function wp_slash( $value ) {
 	if ( is_array( $value ) ) {
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 4c323812991d7..9af7df4b32831 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -31,6 +31,8 @@
  * @param bool   $translate Whether the return date should be translated. Default true.
  * @return string|int|false Integer if `$format` is 'U' or 'G', string otherwise.
  *                          False on failure.
+ *
+ * @phpstan-return ($format is 'G'|'U' ? int|false : string|false)
  */
 function mysql2date( $format, $date, $translate = true ) {
 	if ( empty( $date ) ) {
@@ -74,6 +76,8 @@ function mysql2date( $format, $date, $translate = true ) {
  *                     or PHP date format string (e.g. 'Y-m-d').
  * @param bool   $gmt  Optional. Whether to use GMT timezone. Default false.
  * @return int|string Integer if `$type` is 'timestamp' or 'U', string otherwise.
+ *
+ * @phpstan-return ($type is 'timestamp'|'U' ? int : string)
  */
 function current_time( $type, $gmt = false ) {
 	// Don't use non-GMT timestamp, unless you know the difference and really need to.
@@ -465,6 +469,7 @@ function number_format_i18n( $number, $decimals = 0 ) {
  * @return string|false Number string on success, false on failure.
  *
  * @phpstan-param int|float|numeric-string $bytes
+ * @phpstan-return ( $bytes is int<0, max> ? string : string|false )
  */
 function size_format( $bytes, $decimals = 0 ) {
 	if ( ! is_numeric( $bytes ) ) {
@@ -632,6 +637,10 @@ function get_weekstartend( $mysqlstring, $start_of_week = '' ) {
  *
  * @param string|array|object $data Data that might be serialized.
  * @return mixed A scalar data.
+ *
+ * @phpstan-template T of mixed
+ * @phpstan-param T $data
+ * @phpstan-return (T is array|object|string ? string : T)
  */
 function maybe_serialize( $data ) {
 	if ( is_array( $data ) || is_object( $data ) ) {
@@ -840,6 +849,8 @@ function xmlrpc_removepostdata( $content ) {
  *
  * @param string $content Content to extract URLs from.
  * @return string[] Array of URLs found in passed string.
+ *
+ * @phpstan-return ($content is empty ? array{} : list<string>)
  */
 function wp_extract_urls( $content ) {
 	preg_match_all(
@@ -993,6 +1004,8 @@ function do_enclose( $content, $post ) {
  * @param string $url        URL to retrieve HTTP headers from.
  * @param bool   $deprecated Not Used.
  * @return \WpOrg\Requests\Utility\CaseInsensitiveDictionary|false Headers on success, false on failure.
+ *
+ * @phpstan-param false $deprecated
  */
 function wp_get_http_headers( $url, $deprecated = false ) {
 	if ( ! empty( $deprecated ) ) {
@@ -1022,6 +1035,8 @@ function wp_get_http_headers( $url, $deprecated = false ) {
  * @global string $previousday The day of the previous post in the loop.
  *
  * @return int 1 when new day, 0 if not a new day.
+ *
+ * @phpstan-return 0|1
  */
 function is_new_day() {
 	global $currentday, $previousday;
@@ -1600,6 +1615,9 @@ function get_num_queries() {
  *
  * @param string $yn Character string containing either 'y' (yes) or 'n' (no).
  * @return bool True if 'y', false on anything else.
+ *
+ * @phpstan-pure
+ * @phpstan-return ($yn is 'y' ? true : false)
  */
 function bool_from_yn( $yn ) {
 	return ( 'y' === strtolower( $yn ) );
@@ -1879,6 +1897,8 @@ function is_blog_installed() {
  * @param int|string $action    Optional. Nonce action name. Default -1.
  * @param string     $name      Optional. Nonce name. Default '_wpnonce'.
  * @return string Escaped URL with nonce action added.
+ *
+ * @phpstan-param -1|string $action
  */
 function wp_nonce_url( $actionurl, $action = -1, $name = '_wpnonce' ) {
 	$actionurl = str_replace( '&amp;', '&', $actionurl );
@@ -1910,6 +1930,8 @@ function wp_nonce_url( $actionurl, $action = -1, $name = '_wpnonce' ) {
  * @param bool       $referer Optional. Whether to set the referer field for validation. Default true.
  * @param bool       $display Optional. Whether to display or return hidden form field. Default true.
  * @return string Nonce field HTML markup.
+ *
+ * @phpstan-param -1|string $action
  */
 function wp_nonce_field( $action = -1, $name = '_wpnonce', $referer = true, $display = true ) {
 	$name        = esc_attr( $name );
@@ -2131,6 +2153,9 @@ function wp_mkdir_p( $target ) {
  *
  * @param string $path File path.
  * @return bool True if path is absolute, false is not absolute.
+ *
+ * @phpstan-assert-if-true =non-falsy-string $path
+ * @phpstan-return ($path is non-falsy-string ? bool : false)
  */
 function path_is_absolute( $path ) {
 	/*
@@ -2173,6 +2198,8 @@ function path_is_absolute( $path ) {
  * @param string $base Base path.
  * @param string $path Path relative to $base.
  * @return string The path with the base or absolute path.
+ *
+ * @phpstan-return non-falsy-string
  */
 function path_join( $base, $path ) {
 	if ( path_is_absolute( $path ) ) {
@@ -2939,6 +2966,9 @@ function _wp_check_existing_file_names( $filename, $files ) {
  * }
  * @phpstan-return array{ file: non-empty-string, url: non-empty-string, type: string|false, error: false }
  *                |array{ error: string, ... }
+ *
+ * @phpstan-param non-empty-string $name
+ * @phpstan-param null $deprecated
  */
 function wp_upload_bits( $name, $deprecated, $bits, $time = null ) {
 	if ( ! empty( $deprecated ) ) {
@@ -4459,6 +4489,9 @@ function _wp_die_process_input( $message, $title = '', $args = array() ) {
  * @param int   $depth Optional. Maximum depth to walk through $value. Must be
  *                     greater than 0. Default 512.
  * @return string|false The JSON encoded string, or false if it cannot be encoded.
+ *
+ * @phpstan-param int<1, max> $depth
+ * @phpstan-return non-empty-string|false
  */
 function wp_json_encode( $value, $flags = 0, $depth = 512 ) {
 	$json = json_encode( $value, $flags, $depth );
@@ -5416,6 +5449,8 @@ function _wp_to_kebab_case( $input_string ) {
  * @return bool Whether the variable is a list.
  *
  * @phpstan-assert-if-true array<int, mixed> $data
+ * @phpstan-pure
+ * @phpstan-return ($data is array<int, mixed> ? true : false)
  */
 function wp_is_numeric_array( $data ): bool {
 	if ( ! is_array( $data ) ) {
@@ -6227,6 +6262,8 @@ function _doing_it_wrong( $function_name, $message, $version ) {
  *                              before passing to this function to avoid being stripped {@see wp_kses()}.
  * @param int    $error_level   Optional. The designated error type for this error.
  *                              Only works with E_USER family of constants. Default E_USER_NOTICE.
+ *
+ * @phpstan-param \E_USER_ERROR|\E_USER_WARNING|\E_USER_NOTICE|\E_USER_DEPRECATED $error_level
  */
 function wp_trigger_error( $function_name, $message, $error_level = E_USER_NOTICE ) {
 	/**
@@ -6414,6 +6451,8 @@ function iis7_supports_permalinks() {
  * @param string   $file          File path.
  * @param string[] $allowed_files Optional. Array of allowed files. Default empty array.
  * @return int 0 means nothing is wrong, greater than 0 means something was wrong.
+ *
+ * @phpstan-return ($file is '' ? 0 : ($allowed_files is empty ? 0|1|2 : 0|1|2|3))
  */
 function validate_file( $file, $allowed_files = array() ) {
 	if ( ! is_scalar( $file ) || '' === $file ) {
@@ -7170,6 +7209,8 @@ function __return_false() { // phpcs:ignore WordPress.NamingConventions.ValidFun
  * @since 3.0.0
  *
  * @return int 0.
+ *
+ * @phpstan-return 0
  */
 function __return_zero() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionDoubleUnderscore,PHPCompatibility.FunctionNameRestrictions.ReservedFunctionNames.FunctionDoubleUnderscore
 	return 0;
@@ -7183,6 +7224,8 @@ function __return_zero() { // phpcs:ignore WordPress.NamingConventions.ValidFunc
  * @since 3.0.0
  *
  * @return array Empty array.
+ *
+ * @phpstan-return array{}
  */
 function __return_empty_array() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionDoubleUnderscore,PHPCompatibility.FunctionNameRestrictions.ReservedFunctionNames.FunctionDoubleUnderscore
 	return array();
@@ -7211,6 +7254,8 @@ function __return_null() { // phpcs:ignore WordPress.NamingConventions.ValidFunc
  * @see __return_null()
  *
  * @return string Empty string.
+ *
+ * @phpstan-return ''
  */
 function __return_empty_string() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionDoubleUnderscore,PHPCompatibility.FunctionNameRestrictions.ReservedFunctionNames.FunctionDoubleUnderscore
 	return '';
@@ -7424,6 +7469,8 @@ function wp_allowed_protocols() {
  *                             the raw array returned. Default true.
  * @return string|array Either a string containing a reversed comma separated trace or an array
  *                      of individual calls.
+ *
+ * @phpstan-return ($pretty is true ? string : list<string>)
  */
 function wp_debug_backtrace_summary( $ignore_class = null, $skip_frames = 0, $pretty = true ) {
 	static $truncate_paths;
@@ -7556,6 +7603,8 @@ function _device_can_upload() {
  *
  * @param string $path The resource path or URL.
  * @return bool True if the path is a stream URL.
+ *
+ * @phpstan-assert-if-true =non-falsy-string $path
  */
 function wp_is_stream( $path ) {
 	$scheme_separator = strpos( $path, '://' );
@@ -7733,6 +7782,8 @@ function wp_auth_check( $response ) {
  *
  * @param string $tag An HTML tag name. Example: 'video'.
  * @return string Tag RegEx.
+ *
+ * @phpstan-return ( $tag is ''|'0' ? '' : non-falsy-string )
  */
 function get_tag_regex( $tag ) {
 	if ( empty( $tag ) ) {
@@ -8142,6 +8193,9 @@ function wp_raise_memory_limit( $context = 'admin' ) {
  * @since 7.0.0 Uses wp_rand if available.
  *
  * @return string UUID.
+ *
+ * @phpstan-impure
+ * @phpstan-return lowercase-string&non-falsy-string
  */
 function wp_generate_uuid4() {
 	static $backup_randomizer = false;
@@ -8179,6 +8233,11 @@ function wp_generate_uuid4() {
  * @param int   $version Specify which version of UUID to check against. Default is none,
  *                       to accept any UUID version. Otherwise, only version allowed is `4`.
  * @return bool The string is a valid UUID or false on failure.
+ *
+ * @phpstan-template TUuid of string
+ * @phpstan-param TUuid $uuid
+ * @phpstan-assert-if-true =TUuid&lowercase-string&non-falsy-string $uuid
+ * @phpstan-return ($version is 4|null ? bool : false)
  */
 function wp_is_uuid( $uuid, $version = null ) {
 
@@ -8211,6 +8270,9 @@ function wp_is_uuid( $uuid, $version = null ) {
  *
  * @param string $prefix Prefix for the returned ID.
  * @return string Unique ID.
+ *
+ * @phpstan-impure
+ * @phpstan-return ($prefix is ''|numeric-string ? numeric-string : string)&non-falsy-string&($prefix is lowercase-string ? lowercase-string : string)
  */
 function wp_unique_id( $prefix = '' ) {
 	static $id_counter = 0;
@@ -8230,6 +8292,9 @@ function wp_unique_id( $prefix = '' ) {
  *
  * @param string $prefix Optional. Prefix for the returned ID. Default empty string.
  * @return string Incremental ID per prefix.
+ *
+ * @phpstan-impure
+ * @phpstan-return ($prefix is ''|numeric-string ? numeric-string : string)&non-falsy-string&($prefix is lowercase-string ? lowercase-string : string)
  */
 function wp_unique_prefixed_id( $prefix = '' ) {
 	static $id_counters = array();
@@ -8263,6 +8328,9 @@ function wp_unique_prefixed_id( $prefix = '' ) {
  * @param array  $data   The input array to generate an ID from.
  * @param string $prefix Optional. A prefix to prepend to the generated ID. Default empty string.
  * @return string The generated unique ID for the array.
+ *
+ * @phpstan-param non-empty-array $data
+ * @phpstan-return ($prefix is lowercase-string ? lowercase-string&non-falsy-string : non-falsy-string)
  */
 function wp_unique_id_from_values( array $data, string $prefix = '' ): string {
 	if ( empty( $data ) ) {
@@ -9160,6 +9228,8 @@ function clean_dirsize_cache( $path ) {
  * @since 6.7.0
  *
  * @return string The current WordPress version.
+ *
+ * @phpstan-return non-falsy-string
  */
 function wp_get_wp_version() {
 	static $wp_version;
@@ -9427,6 +9497,8 @@ function wp_is_heic_image_mime_type( $mime_type ) {
  *
  * @param string $message The message to hash.
  * @return string The hash of the message.
+ *
+ * @phpstan-return non-falsy-string
  */
 function wp_fast_hash(
 	#[\SensitiveParameter]
diff --git a/src/wp-includes/general-template.php b/src/wp-includes/general-template.php
index 63a3aa67123b2..df763b77a2f3d 100644
--- a/src/wp-includes/general-template.php
+++ b/src/wp-includes/general-template.php
@@ -1901,6 +1901,8 @@ function single_term_title( $prefix = '', $display = true ) {
  * @param string $prefix  Optional. What to display before the title.
  * @param bool   $display Optional. Whether to display or retrieve title. Default true.
  * @return string|false|null False if there's no valid title for the month. Title when retrieving.
+ *
+ * @phpstan-return ( $display is true ? false|null : false|string )
  */
 function single_month_title( $prefix = '', $display = true ) {
 	global $wp_locale;
@@ -4913,6 +4915,12 @@ function language_attributes( $doctype = 'html' ) {
  * }
  * @return string|string[]|null String of page links or array of page links, depending on 'type' argument.
  *                              Null if total number of pages is less than 2.
+ *
+ * @phpstan-return (
+ *     $args is array{total: int<min, 1>, ...}
+ *         ? null
+ *         : ($args is array{type: 'array', ...} ? list<string> : string)
+ * )
  */
 function paginate_links( $args = '' ) {
 	global $wp_query, $wp_rewrite;
diff --git a/src/wp-includes/http.php b/src/wp-includes/http.php
index c2855a8d8d9c1..98b6cf174a367 100644
--- a/src/wp-includes/http.php
+++ b/src/wp-includes/http.php
@@ -48,6 +48,15 @@ function _wp_http_get_object() {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_safe_remote_request( $url, $args = array() ) {
 	$args['reject_unsafe_urls'] = true;
@@ -77,6 +86,15 @@ function wp_safe_remote_request( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_safe_remote_get( $url, $args = array() ) {
 	$args['reject_unsafe_urls'] = true;
@@ -106,6 +124,15 @@ function wp_safe_remote_get( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_safe_remote_post( $url, $args = array() ) {
 	$args['reject_unsafe_urls'] = true;
@@ -135,6 +162,15 @@ function wp_safe_remote_post( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_safe_remote_head( $url, $args = array() ) {
 	$args['reject_unsafe_urls'] = true;
@@ -162,6 +198,15 @@ function wp_safe_remote_head( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response array or a WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_remote_request( $url, $args = array() ) {
 	$http = _wp_http_get_object();
@@ -183,6 +228,15 @@ function wp_remote_request( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_remote_get( $url, $args = array() ) {
 	$http = _wp_http_get_object();
@@ -204,6 +258,15 @@ function wp_remote_get( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_remote_post( $url, $args = array() ) {
 	$http = _wp_http_get_object();
@@ -225,6 +288,15 @@ function wp_remote_post( $url, $args = array() ) {
  *                     See WP_Http::request() for information on accepted arguments.
  * @return array|WP_Error The response or WP_Error on failure.
  *                        See WP_Http::request() for information on return value.
+ *
+ * @phpstan-return array{
+ *     headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary,
+ *     body: string,
+ *     response: array{code: int, message: string},
+ *     cookies: array<int, WP_Http_Cookie>,
+ *     filename: string|null,
+ *     http_response: WP_HTTP_Requests_Response,
+ * }|WP_Error
  */
 function wp_remote_head( $url, $args = array() ) {
 	$http = _wp_http_get_object();
@@ -555,6 +627,10 @@ function send_origin_headers() {
  *
  * @param string $url Request URL.
  * @return string|false Returns false if the URL is not safe, or the original URL if it is safe.
+ *
+ * @phpstan-template TUrl of string
+ * @phpstan-param TUrl $url
+ * @phpstan-return (TUrl is numeric|'' ? false : TUrl|false)
  */
 function wp_http_validate_url( $url ) {
 	if ( ! is_string( $url ) || '' === $url || is_numeric( $url ) ) {
diff --git a/src/wp-includes/kses.php b/src/wp-includes/kses.php
index 9394b75989912..ed04ad1878ad1 100644
--- a/src/wp-includes/kses.php
+++ b/src/wp-includes/kses.php
@@ -2643,6 +2643,8 @@ function kses_init() {
  * @param string $css        A string of CSS rules, decoded from an HTML `style` attribute.
  * @param string $deprecated Not used.
  * @return string Filtered string of CSS rules, needing HTML escaping before sending back to a `style` attribute.
+ *
+ * @phpstan-param '' $deprecated
  */
 function safecss_filter_attr( $css, $deprecated = '' ) {
 	if ( ! empty( $deprecated ) ) {
diff --git a/src/wp-includes/l10n.php b/src/wp-includes/l10n.php
index 7b9d2652d41dd..95c41fb3f6bdc 100644
--- a/src/wp-includes/l10n.php
+++ b/src/wp-includes/l10n.php
@@ -995,6 +995,8 @@ function load_default_textdomain( $locale = null ) {
  * @param string|false $plugin_rel_path Optional. Relative path to WP_PLUGIN_DIR where the .mo file resides.
  *                                      Default false.
  * @return bool True when textdomain is successfully loaded, false otherwise.
+ *
+ * @phpstan-param false $deprecated
  */
 function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path = false ) {
 	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
@@ -2066,6 +2068,8 @@ function wp_get_list_item_separator() {
  *
  * @return string Locale-specific word count type. Possible values are `characters_excluding_spaces`,
  *                `characters_including_spaces`, or `words`. Defaults to `words`.
+ *
+ * @phpstan-return 'characters_excluding_spaces'|'characters_including_spaces'|'words'
  */
 function wp_get_word_count_type() {
 	global $wp_locale;
diff --git a/src/wp-includes/l10n/class-wp-translations.php b/src/wp-includes/l10n/class-wp-translations.php
index e919fea8b94b3..b158501b64e83 100644
--- a/src/wp-includes/l10n/class-wp-translations.php
+++ b/src/wp-includes/l10n/class-wp-translations.php
@@ -112,6 +112,11 @@ private function make_entry( $original, $translations ): Translation_Entry {
 	 * @param int|float   $count    Count. Should be an integer, but some plugins pass floats.
 	 * @param string|null $context  Context.
 	 * @return string|null Translation if it exists, or the unchanged singular string.
+	 *
+	 * @phpstan-template T of string|null
+	 * @phpstan-param T $singular
+	 * @phpstan-param int $count
+	 * @phpstan-return ($singular is null ? null : ($plural is null ? T : string))
 	 */
 	public function translate_plural( $singular, $plural, $count = 1, $context = '' ) {
 		if ( null === $singular || null === $plural ) {
@@ -135,6 +140,8 @@ public function translate_plural( $singular, $plural, $count = 1, $context = ''
 	 * @param string|null $singular Singular string.
 	 * @param string|null $context  Context.
 	 * @return string|null Translation if it exists, or the unchanged singular string
+	 *
+	 * @phpstan-return ($singular is null ? null : string)
 	 */
 	public function translate( $singular, $context = '' ) {
 		if ( null === $singular ) {
diff --git a/src/wp-includes/link-template.php b/src/wp-includes/link-template.php
index 10bda681154f9..1dd869dfae709 100644
--- a/src/wp-includes/link-template.php
+++ b/src/wp-includes/link-template.php
@@ -153,6 +153,8 @@ function wp_force_plain_post_permalink( $post = null, $sample = null ) {
  * @param int|WP_Post $post      Optional. Post ID or post object. Default is the global `$post`.
  * @param bool        $leavename Optional. Whether to keep post name or page name. Default false.
  * @return string|false The permalink URL. False if the post does not exist.
+ *
+ * @phpstan-return ($post is WP_Post ? string : string|false)
  */
 function get_the_permalink( $post = 0, $leavename = false ) {
 	return get_permalink( $post, $leavename );
@@ -166,6 +168,8 @@ function get_the_permalink( $post = 0, $leavename = false ) {
  * @param int|WP_Post $post      Optional. Post ID or post object. Default is the global `$post`.
  * @param bool        $leavename Optional. Whether to keep post name or page name. Default false.
  * @return string|false The permalink URL. False if the post does not exist.
+ *
+ * @phpstan-return ($post is WP_Post ? string : string|false)
  */
 function get_permalink( $post = 0, $leavename = false ) {
 	$rewritecode = array(
@@ -320,6 +324,8 @@ function get_permalink( $post = 0, $leavename = false ) {
  * @param bool        $leavename Optional. Whether to keep post name. Default false.
  * @param bool        $sample    Optional. Is it a sample permalink. Default false.
  * @return string|false The post permalink URL. False if the post does not exist.
+ *
+ * @phpstan-return ($post is WP_Post ? string : string|false)
  */
 function get_post_permalink( $post = 0, $leavename = false, $sample = false ) {
 	global $wp_rewrite;
@@ -1554,6 +1560,8 @@ function edit_post_link( $text = null, $before = '', $after = '', $post = 0, $cs
  * @param string      $deprecated   Not used.
  * @param bool        $force_delete Optional. Whether to bypass Trash and force deletion. Default false.
  * @return string|null The delete post link URL for the given post.
+ *
+ * @phpstan-param '' $deprecated
  */
 function get_delete_post_link( $post = 0, $deprecated = '', $force_delete = false ) {
 	if ( ! empty( $deprecated ) ) {
@@ -4881,6 +4889,8 @@ function get_the_privacy_policy_link( $before = '', $after = '' ) {
  * @since 6.2.0
  *
  * @return string[] An array of URL hosts.
+ *
+ * @phpstan-return array<lowercase-string>
  */
 function wp_internal_hosts() {
 	static $internal_hosts;
diff --git a/src/wp-includes/load.php b/src/wp-includes/load.php
index 9d407453424c5..1846b04573110 100644
--- a/src/wp-includes/load.php
+++ b/src/wp-includes/load.php
@@ -11,6 +11,8 @@
  * @since 4.4.0
  *
  * @return string The HTTP protocol. Default: HTTP/1.0.
+ *
+ * @phpstan-return 'HTTP/1.0'|'HTTP/1.1'|'HTTP/2'|'HTTP/2.0'|'HTTP/3'
  */
 function wp_get_server_protocol() {
 	$protocol = $_SERVER['SERVER_PROTOCOL'] ?? '';
@@ -1464,6 +1466,31 @@ function is_multisite() {
  *
  * @param mixed $maybeint Data you wish to have converted to a non-negative integer.
  * @return int A non-negative integer.
+ *
+ * @phpstan-template T of int
+ * @phpstan-param T|scalar|array|resource|null $maybeint
+ * @phpstan-pure
+ * @phpstan-return (
+ *     $maybeint is T&int<0, max>
+ *         ? T
+ *         : (
+ *             $maybeint is int<min, -1>
+ *                 ? int<1, max>
+ *                 : (
+ *                     $maybeint is empty
+ *                         ? 0
+ *                         : (
+ *                             $maybeint is numeric-string
+ *                                 ? int<0, max>
+ *                                 : (
+ *                                     $maybeint is string
+ *                                         ? 0
+ *                                         : ($maybeint is true|non-empty-array ? 1 : ($maybeint is bool ? 0|1 : int<0, max>))
+ *                                 )
+ *                         )
+ *                 )
+ *         )
+ * )
  */
 function absint( $maybeint ) {
 	return abs( (int) $maybeint );
@@ -1477,6 +1504,8 @@ function absint( $maybeint ) {
  * @global int $blog_id
  *
  * @return int Site ID.
+ *
+ * @phpstan-return int<0, max>
  */
 function get_current_blog_id() {
 	global $blog_id;
@@ -1800,6 +1829,7 @@ function wp_doing_cron() {
  * @return bool Whether the variable is an instance of WP_Error.
  *
  * @phpstan-assert-if-true WP_Error $thing
+ * @phpstan-return ($thing is WP_Error ? true : false)
  */
 function is_wp_error( $thing ) {
 	$is_wp_error = ( $thing instanceof WP_Error );
diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index be0b2fbf098cc..daa2b5e8cfc1b 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -3699,11 +3699,12 @@ function wp_audio_shortcode( $attr, $content = '' ) {
 	 *
 	 * @since 3.6.0
 	 *
-	 * @param string $html    Audio shortcode HTML output.
-	 * @param array  $atts    Array of audio shortcode attributes.
-	 * @param string $audio   Audio file.
-	 * @param int    $post_id Post ID.
-	 * @param string $library Media library used for the audio shortcode.
+	 * @param string       $html    Audio shortcode HTML output.
+	 * @param array        $atts    Array of audio shortcode attributes.
+	 * @param WP_Post|null $audio   Audio attachment post when the shortcode has no source and
+	 *                              an attached audio file is used, null otherwise.
+	 * @param int          $post_id Post ID.
+	 * @param string       $library Media library used for the audio shortcode.
 	 */
 	return apply_filters( 'wp_audio_shortcode', $html, $atts, $audio, $post_id, $library );
 }
@@ -3994,11 +3995,12 @@ function wp_video_shortcode( $attr, $content = '' ) {
 	 *
 	 * @since 3.6.0
 	 *
-	 * @param string $output  Video shortcode HTML output.
-	 * @param array  $atts    Array of video shortcode attributes.
-	 * @param string $video   Video file.
-	 * @param int    $post_id Post ID.
-	 * @param string $library Media library used for the video shortcode.
+	 * @param string       $output  Video shortcode HTML output.
+	 * @param array        $atts    Array of video shortcode attributes.
+	 * @param WP_Post|null $video   Video attachment post when the shortcode has no source and
+	 *                              an attached video file is used, null otherwise.
+	 * @param int          $post_id Post ID.
+	 * @param string       $library Media library used for the video shortcode.
 	 */
 	return apply_filters( 'wp_video_shortcode', $output, $atts, $video, $post_id, $library );
 }
@@ -4072,7 +4074,7 @@ function next_image_link( $size = 'thumbnail', $text = false ) {
  * @param bool         $prev Optional. Whether to display the next (false) or previous (true) link. Default true.
  * @param string|int[] $size Optional. Image size. Accepts any registered image size name, or an array
  *                           of width and height values in pixels (in that order). Default 'thumbnail'.
- * @param bool         $text Optional. Link text. Default false.
+ * @param string|false $text Optional. Link text. Default false.
  * @return string Markup for image link.
  */
 function get_adjacent_image_link( $prev = true, $size = 'thumbnail', $text = false ) {
@@ -4128,7 +4130,7 @@ function get_adjacent_image_link( $prev = true, $size = 'thumbnail', $text = fal
 	 * @param int          $attachment_id Attachment ID
 	 * @param string|int[] $size          Requested image size. Can be any registered image size name, or
 	 *                                    an array of width and height values in pixels (in that order).
-	 * @param string       $text          Link text.
+	 * @param string|false $text          Link text, or false for the image itself.
 	 */
 	return apply_filters( "{$adjacent}_image_link", $output, $attachment_id, $size, $text );
 }
@@ -4143,7 +4145,7 @@ function get_adjacent_image_link( $prev = true, $size = 'thumbnail', $text = fal
  * @param bool         $prev Optional. Whether to display the next (false) or previous (true) link. Default true.
  * @param string|int[] $size Optional. Image size. Accepts any registered image size name, or an array
  *                           of width and height values in pixels (in that order). Default 'thumbnail'.
- * @param bool         $text Optional. Link text. Default false.
+ * @param string|false $text Optional. Link text. Default false.
  */
 function adjacent_image_link( $prev = true, $size = 'thumbnail', $text = false ) {
 	echo get_adjacent_image_link( $prev, $size, $text );
diff --git a/src/wp-includes/meta.php b/src/wp-includes/meta.php
index 577785c2163a0..00ce37323ce4d 100644
--- a/src/wp-includes/meta.php
+++ b/src/wp-includes/meta.php
@@ -266,6 +266,7 @@ function update_metadata( $meta_type, $object_id, $meta_key, $meta_value, $prev_
 	if ( empty( $meta_ids ) ) {
 		return add_metadata( $meta_type, $object_id, $raw_meta_key, $passed_value );
 	}
+	$meta_ids = array_map( 'intval', $meta_ids );
 
 	$_meta_value = $meta_value;
 	$meta_value  = maybe_serialize( $meta_value );
@@ -1431,6 +1432,8 @@ function sanitize_meta( $meta_key, $meta_value, $object_type, $object_subtype =
  * @return bool True if the meta key was successfully registered in the global array, false if not.
  *              Registering a meta key with distinct sanitize and auth callbacks will fire those callbacks,
  *              but will not add to the global registry.
+ *
+ * @phpstan-param null $deprecated
  */
 function register_meta( $object_type, $meta_key, $args, $deprecated = null ) {
 	global $wp_meta_keys;
diff --git a/src/wp-includes/ms-blogs.php b/src/wp-includes/ms-blogs.php
index c54563fbbd2b8..5464f6334c6d8 100644
--- a/src/wp-includes/ms-blogs.php
+++ b/src/wp-includes/ms-blogs.php
@@ -265,7 +265,8 @@ function get_blog_details( $fields = null, $get_all = true ) {
 	 * @since MU (3.0.0)
 	 * @deprecated 4.7.0 Use {@see 'site_details'} instead.
 	 *
-	 * @param WP_Site $details The blog details.
+	 * @param WP_Site|stdClass $details The blog details: a WP_Site from get_blog_details(), or a plain
+	 *                                  object copy of one from WP_Site::get_details().
 	 */
 	$details = apply_filters_deprecated( 'blog_details', array( $details ), '4.7.0', 'site_details' );
 
@@ -456,6 +457,8 @@ function delete_blog_option( $id, $option ) {
  * @param mixed  $value      The option value.
  * @param mixed  $deprecated Not used.
  * @return bool True if the value was updated, false otherwise.
+ *
+ * @phpstan-param null $deprecated
  */
 function update_blog_option( $id, $option, $value, $deprecated = null ) {
 	$id = (int) $id;
@@ -496,6 +499,8 @@ function update_blog_option( $id, $option, $value, $deprecated = null ) {
  * @param int  $new_blog_id The ID of the blog to switch to. Default: current blog.
  * @param bool $deprecated  Not used.
  * @return true Always returns true.
+ *
+ * @phpstan-param null $deprecated
  */
 function switch_to_blog( $new_blog_id, $deprecated = null ) {
 	global $wpdb;
@@ -819,6 +824,8 @@ function get_blog_status( $id, $pref ) {
  *                          Can be used for pagination. Default 0.
  * @param int   $quantity   Optional. The maximum number of blogs to retrieve. Default 40.
  * @return array The list of blogs.
+ *
+ * @phpstan-param '' $deprecated
  */
 function get_last_updated( $deprecated = '', $start = 0, $quantity = 40 ) {
 	global $wpdb;
diff --git a/src/wp-includes/ms-default-filters.php b/src/wp-includes/ms-default-filters.php
index 8682d48e18e45..439683a80c89a 100644
--- a/src/wp-includes/ms-default-filters.php
+++ b/src/wp-includes/ms-default-filters.php
@@ -23,9 +23,12 @@
 // Users.
 add_filter( 'wpmu_validate_user_signup', 'signup_nonce_check' );
 add_action( 'init', 'maybe_add_existing_user_to_blog' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wpmu_new_user', 'newuser_notify_siteadmin' );
 add_action( 'wpmu_activate_user', 'add_new_user_to_blog', 10, 3 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wpmu_activate_user', 'wpmu_welcome_user_notification', 10, 3 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'after_signup_user', 'wpmu_signup_user_notification', 10, 4 );
 add_action( 'network_site_new_created_user', 'wp_send_new_user_notifications' );
 add_action( 'network_site_users_created_user', 'wp_send_new_user_notifications' );
@@ -38,7 +41,9 @@
 
 // Blogs.
 add_filter( 'wpmu_validate_blog_signup', 'signup_nonce_check' );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wpmu_activate_blog', 'wpmu_welcome_notification', 10, 5 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'after_signup_site', 'wpmu_signup_blog_notification', 10, 7 );
 add_filter( 'wp_normalize_site_data', 'wp_normalize_site_data', 10, 1 );
 add_action( 'wp_validate_site_data', 'wp_validate_site_data', 10, 3 );
@@ -48,9 +53,12 @@
 add_action( 'wp_insert_site', 'wp_maybe_transition_site_statuses_on_update', 10, 1 );
 add_action( 'wp_update_site', 'wp_maybe_transition_site_statuses_on_update', 10, 2 );
 add_action( 'wp_update_site', 'wp_maybe_clean_new_site_cache_on_update', 10, 2 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_initialize_site', 'wp_initialize_site', 10, 2 );
 add_action( 'wp_initialize_site', 'wpmu_log_new_registrations', 100, 2 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_initialize_site', 'newblog_notify_siteadmin', 100, 1 );
+// @phpstan-ignore return.void (WordPress discards an action callback's return value.)
 add_action( 'wp_uninitialize_site', 'wp_uninitialize_site', 10, 1 );
 add_action( 'update_blog_public', 'wp_update_blog_public_option_on_site_update', 1, 2 );
 
diff --git a/src/wp-includes/ms-functions.php b/src/wp-includes/ms-functions.php
index 81dda98f3e312..46fe2537d8521 100644
--- a/src/wp-includes/ms-functions.php
+++ b/src/wp-includes/ms-functions.php
@@ -1478,6 +1478,8 @@ function wpmu_create_blog( $domain, $path, $title, $user_id, $options = array(),
  * @param WP_Site|int $blog_id    The new site's object or ID.
  * @param string      $deprecated Not used.
  * @return bool
+ *
+ * @phpstan-param '' $deprecated
  */
 function newblog_notify_siteadmin( $blog_id, $deprecated = '' ) {
 	if ( is_object( $blog_id ) ) {
@@ -2088,6 +2090,8 @@ function check_upload_mimes( $mimes ) {
  * @global wpdb $wpdb WordPress database abstraction object.
  *
  * @param string $deprecated Not used.
+ *
+ * @phpstan-param '' $deprecated
  */
 function update_posts_count( $deprecated = '' ) {
 	global $wpdb;
@@ -2142,6 +2146,8 @@ function wpmu_log_new_registrations( $blog_id, $user_id ) {
  *
  *     @type string $0 The current site's domain.
  * }
+ *
+ * @phpstan-param '' $deprecated
  */
 function redirect_this_site( $deprecated = '' ) {
 	return array( get_network()->domain );
diff --git a/src/wp-includes/ms-site.php b/src/wp-includes/ms-site.php
index 6399dab72e881..02e227ee7abb4 100644
--- a/src/wp-includes/ms-site.php
+++ b/src/wp-includes/ms-site.php
@@ -441,6 +441,12 @@ function update_sitemeta_cache( $site_ids ) {
  *                           for information on accepted arguments. Default empty array.
  * @return WP_Site[]|int[]|int List of WP_Site objects, a list of site IDs when 'fields' is set to 'ids',
  *                             or the number of sites when 'count' is passed as a query var.
+ *
+ * @phpstan-return (
+ *     $args is array{count: true, ...}
+ *         ? int
+ *         : ($args is array{fields: 'ids', ...} ? array<int, int> : array<int, WP_Site>)
+ * )
  */
 function get_sites( $args = array() ) {
 	$query = new WP_Site_Query();
diff --git a/src/wp-includes/nav-menu.php b/src/wp-includes/nav-menu.php
index ed49892ac0eb6..269a26b5c50d5 100644
--- a/src/wp-includes/nav-menu.php
+++ b/src/wp-includes/nav-menu.php
@@ -86,6 +86,8 @@ function is_nav_menu( $menu ) {
  * @global array $_wp_registered_nav_menus
  *
  * @param string[] $locations Associative array of menu location identifiers (like a slug) and descriptive text.
+ *
+ * @phpstan-param array<string, string> $locations
  */
 function register_nav_menus( $locations = array() ) {
 	global $_wp_registered_nav_menus;
diff --git a/src/wp-includes/option.php b/src/wp-includes/option.php
index d5c179c645af3..f32f518d35580 100644
--- a/src/wp-includes/option.php
+++ b/src/wp-includes/option.php
@@ -1065,6 +1065,8 @@ function update_option( $option, $value, $autoload = null ) {
  *                              to not autoload them, by using false.
  *                              Default is null, which means WordPress will determine the autoload value.
  * @return bool True if the option was added, false otherwise.
+ *
+ * @phpstan-param '' $deprecated
  */
 function add_option( $option, $value = '', $deprecated = '', $autoload = null ) {
 	global $wpdb;
@@ -1427,6 +1429,8 @@ function delete_transient( $transient ) {
  *
  * @param string $transient Transient name. Expected to not be SQL-escaped.
  * @return mixed Value of transient.
+ *
+ * @phpstan-impure
  */
 function get_transient( $transient ) {
 
@@ -1930,6 +1934,8 @@ function delete_all_user_settings() {
  * @param mixed  $default_value Optional. Value to return if the option doesn't exist. Default false.
  * @param bool   $deprecated    Whether to use cache. Multisite only. Always set to true.
  * @return mixed Value set for the option.
+ *
+ * @phpstan-param true $deprecated
  */
 function get_site_option( $option, $default_value = false, $deprecated = true ) {
 	return get_network_option( null, $option, $default_value );
@@ -3119,6 +3125,8 @@ function register_setting( $option_group, $option_name, $args = array() ) {
  * @param string   $option_group The settings group name used during registration.
  * @param string   $option_name  The name of the option to unregister.
  * @param callable $deprecated   Optional. Deprecated.
+ *
+ * @phpstan-param '' $deprecated
  */
 function unregister_setting( $option_group, $option_name, $deprecated = '' ) {
 	global $new_allowed_options, $wp_registered_settings;
diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index aa39c31d78ce5..ac99a9742117b 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -97,6 +97,8 @@ function get_userdata( $user_id ) {
 	 * @param string     $field The field to retrieve the user with. id | ID | slug | email | login.
 	 * @param int|string $value A value for $field. A user ID, slug, email address, or login name.
 	 * @return WP_User|false WP_User object on success, false on failure.
+	 *
+	 * @phpstan-return ($field is 'id'|'ID' ? ($value is int<min, 0> ? false : WP_User|false) : WP_User|false)
 	 */
 	function get_user_by( $field, $value ) {
 		$userdata = WP_User::get_data_by( $field, $value );
@@ -185,6 +187,8 @@ function cache_users( $user_ids ) {
 	 * @param string|string[] $attachments Optional. Paths to files to attach.
 	 * @param string|string[] $embeds      Optional. Paths to files to embed.
 	 * @return bool Whether the email was sent successfully.
+	 *
+	 * @phpstan-impure
 	 */
 	function wp_mail( $to, $subject, $message, $headers = '', $attachments = array(), $embeds = array() ) {
 		// Compact the input, apply the filters, and extract them back out.
@@ -2440,6 +2444,9 @@ function wp_new_user_notification( $user_id, $deprecated = null, $notify = '' )
 	 *
 	 * @param string|int $action Optional. The nonce action. Default -1.
 	 * @return float Float value rounded up to the next highest integer.
+	 *
+	 * @phpstan-param -1|string $action
+	 * @phpstan-impure
 	 */
 	function wp_nonce_tick( $action = -1 ) {
 		/**
@@ -2470,6 +2477,9 @@ function wp_nonce_tick( $action = -1 ) {
 	 * @return int|false 1 if the nonce is valid and generated between 0-12 hours ago,
 	 *                   2 if the nonce is valid and generated between 12-24 hours ago.
 	 *                   False if the nonce is invalid.
+	 *
+	 * @phpstan-param -1|string $action
+	 * @phpstan-return 1|2|false
 	 */
 	function wp_verify_nonce( $nonce, $action = -1 ) {
 		$nonce = (string) $nonce;
@@ -2533,6 +2543,9 @@ function wp_verify_nonce( $nonce, $action = -1 ) {
 	 *
 	 * @param string|int $action Scalar value to add context to the nonce.
 	 * @return string The token.
+	 *
+	 * @phpstan-param -1|string $action
+	 * @phpstan-return lowercase-string&non-falsy-string
 	 */
 	function wp_create_nonce( $action = -1 ) {
 		$user = wp_get_current_user();
@@ -2715,6 +2728,9 @@ function wp_salt( $scheme = 'auth' ) {
 	 * @param string $scheme Authentication scheme (auth, secure_auth, logged_in, nonce).
 	 * @param string $algo   Hashing algorithm to use. Default: 'md5'.
 	 * @return string Hash of $data.
+	 *
+	 * @phpstan-param 'auth'|'logged_in'|'nonce'|'secure_auth' $scheme
+	 * @phpstan-return lowercase-string&non-falsy-string
 	 */
 	function wp_hash( $data, $scheme = 'auth', $algo = 'md5' ) {
 		$salt = wp_salt( $scheme );
@@ -2960,6 +2976,8 @@ function wp_password_needs_rehash( $hash, $user_id = '' ) {
 	 * @param bool $extra_special_chars Optional. Whether to include other special characters.
 	 *                                  Used when generating secret keys and salts. Default false.
 	 * @return string The random password.
+	 *
+	 * @phpstan-impure
 	 */
 	function wp_generate_password( $length = 12, $special_chars = true, $extra_special_chars = false ) {
 		$chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
@@ -3005,6 +3023,8 @@ function wp_generate_password( $length = 12, $special_chars = true, $extra_speci
 	 * @param int $max Optional. Upper limit for the generated number.
 	 *                 Accepts positive integers. Defaults to 4294967295.
 	 * @return int A random non-negative number between min and max.
+	 *
+	 * @phpstan-impure
 	 */
 	function wp_rand( $min = null, $max = null ) {
 		global $rnd_value;
diff --git a/src/wp-includes/plugin.php b/src/wp-includes/plugin.php
index 38e88aa96bb00..10e40626265a7 100644
--- a/src/wp-includes/plugin.php
+++ b/src/wp-includes/plugin.php
@@ -171,6 +171,8 @@ function add_filter( $hook_name, $callback, $priority = 10, $accepted_args = 1 )
  * @param mixed  ...$args   Optional. Additional parameters to pass to the callback functions.
  * @no-named-arguments
  * @return mixed The filtered value after all hooked functions are applied to it.
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function apply_filters( $hook_name, $value, ...$args ) {
 	global $wp_filter, $wp_filters, $wp_current_filter;
@@ -226,6 +228,8 @@ function apply_filters( $hook_name, $value, ...$args ) {
  * @param string                $hook_name The name of the filter hook.
  * @param non-empty-list<mixed> $args      The arguments supplied to the functions hooked to `$hook_name`.
  * @return mixed The filtered value after all hooked functions are applied to it.
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function apply_filters_ref_array( $hook_name, $args ) {
 	global $wp_filter, $wp_filters, $wp_current_filter;
@@ -285,6 +289,7 @@ function apply_filters_ref_array( $hook_name, $args ) {
  *                  If `$callback` and `$priority` are both provided, a boolean is returned
  *                  for whether the specific function is registered at that priority.
  * @phpstan-param Maybe_Callable|false $callback
+ * @phpstan-return ($callback is false ? bool : false|int)
  */
 function has_filter( $hook_name, $callback = false, $priority = false ) {
 	global $wp_filter;
@@ -369,6 +374,8 @@ function remove_all_filters( $hook_name, $priority = false ) {
  * @global string[] $wp_current_filter Stores the list of current filters with the current one last
  *
  * @return string|false Hook name of the current filter, false if no filter is running.
+ *
+ * @phpstan-return non-empty-string|false
  */
 function current_filter() {
 	global $wp_current_filter;
@@ -416,6 +423,8 @@ function doing_filter( $hook_name = null ) {
  *
  * @param string $hook_name The name of the filter hook.
  * @return int The number of times the filter hook has been applied.
+ *
+ * @phpstan-return int<0, max>
  */
 function did_filter( $hook_name ) {
 	global $wp_filters;
@@ -488,6 +497,8 @@ function add_action( $hook_name, $callback, $priority = 10, $accepted_args = 1 )
  * @param mixed  ...$arg    Optional. Additional arguments which are passed on to the
  *                          functions hooked to the action. Default empty.
  * @no-named-arguments
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function do_action( $hook_name, ...$arg ) {
 	global $wp_filter, $wp_actions, $wp_current_filter;
@@ -543,6 +554,8 @@ function do_action( $hook_name, ...$arg ) {
  *
  * @param string      $hook_name The name of the action to be executed.
  * @param list<mixed> $args      The arguments supplied to the functions hooked to `$hook_name`.
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function do_action_ref_array( $hook_name, $args ) {
 	global $wp_filter, $wp_actions, $wp_current_filter;
@@ -600,6 +613,7 @@ function do_action_ref_array( $hook_name, $args ) {
  *                  If `$callback` and `$priority` are both provided, a boolean is returned
  *                  for whether the specific function is registered at that priority.
  * @phpstan-param Maybe_Callable|false $callback
+ * @phpstan-return ($callback is false ? bool : false|int)
  */
 function has_action( $hook_name, $callback = false, $priority = false ) {
 	return has_filter( $hook_name, $callback, $priority );
@@ -650,6 +664,8 @@ function remove_all_actions( $hook_name, $priority = false ) {
  * @since 3.9.0
  *
  * @return string|false Hook name of the current action, false if no action is running.
+ *
+ * @phpstan-return non-empty-string|false
  */
 function current_action() {
 	return current_filter();
@@ -688,6 +704,8 @@ function doing_action( $hook_name = null ) {
  *
  * @param string $hook_name The name of the action hook.
  * @return int The number of times the action hook has been fired.
+ *
+ * @phpstan-return int<0, max>
  */
 function did_action( $hook_name ) {
 	global $wp_actions;
@@ -725,6 +743,8 @@ function did_action( $hook_name ) {
  * @param string                $replacement Optional. The hook that should have been used. Default empty.
  * @param string                $message     Optional. A message regarding the change. Default empty.
  * @return mixed The filtered value after all hooked functions are applied to it.
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function apply_filters_deprecated( $hook_name, $args, $version, $replacement = '', $message = '' ) {
 	if ( ! has_filter( $hook_name ) ) {
@@ -752,6 +772,8 @@ function apply_filters_deprecated( $hook_name, $args, $version, $replacement = '
  * @param string      $version     The version of WordPress that deprecated the hook.
  * @param string      $replacement Optional. The hook that should have been used. Default empty.
  * @param string      $message     Optional. A message regarding the change. Default empty.
+ *
+ * @phpstan-param non-empty-string $hook_name
  */
 function do_action_deprecated( $hook_name, $args, $version, $replacement = '', $message = '' ) {
 	if ( ! has_action( $hook_name ) ) {
@@ -882,6 +904,9 @@ function plugin_dir_url( $file ) {
  *
  * @param string   $file     The filename of the plugin including the path.
  * @param callable $callback The function hooked to the 'activate_PLUGIN' action.
+ *
+ * @phpstan-param callable(bool): void $callback
+ * @phpstan-return void
  */
 function register_activation_hook( $file, $callback ) {
 	$file = plugin_basename( $file );
@@ -905,6 +930,9 @@ function register_activation_hook( $file, $callback ) {
  *
  * @param string   $file     The filename of the plugin including the path.
  * @param callable $callback The function hooked to the 'deactivate_PLUGIN' action.
+ *
+ * @phpstan-param callable(bool): void $callback
+ * @phpstan-return void
  */
 function register_deactivation_hook( $file, $callback ) {
 	$file = plugin_basename( $file );
@@ -936,6 +964,8 @@ function register_deactivation_hook( $file, $callback ) {
  * @param string   $file     Plugin file.
  * @param callable $callback The callback to run when the hook is called. Must be
  *                           a static method or function.
+ *
+ * @phpstan-param callable(): void $callback
  */
 function register_uninstall_hook( $file, $callback ) {
 	if ( is_array( $callback ) && is_object( $callback[0] ) ) {
diff --git a/src/wp-includes/post-template.php b/src/wp-includes/post-template.php
index 86ea3eca58271..3fefee51600bf 100644
--- a/src/wp-includes/post-template.php
+++ b/src/wp-includes/post-template.php
@@ -1637,6 +1637,8 @@ function walk_page_dropdown_tree( ...$args ) {
  * @param bool        $fullsize   Optional. Whether to use full size. Default false.
  * @param bool        $deprecated Deprecated. Not used.
  * @param bool        $permalink  Optional. Whether to include permalink. Default false.
+ *
+ * @phpstan-param false $deprecated
  */
 function the_attachment_link( $post = 0, $fullsize = false, $deprecated = false, $permalink = false ) {
 	if ( ! empty( $deprecated ) ) {
@@ -2051,6 +2053,8 @@ function wp_post_revision_title_expanded( $revision, $link = true ) {
  *
  * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
  * @param string      $type 'all' (default), 'revision' or 'autosave'
+ *
+ * @phpstan-param 'all'|'revision'|'autosave' $type
  */
 function wp_list_post_revisions( $post = 0, $type = 'all' ) {
 	$post = get_post( $post );
diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index aeea4e5bafac2..3190d38d8d68f 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -1828,6 +1828,8 @@ function get_post_types( $args = array(), $output = 'names', $operator = 'and' )
  * }
  * @return WP_Post_Type|WP_Error The registered post type object on success,
  *                               WP_Error object on failure.
+ *
+ * @phpstan-param lowercase-string&non-empty-string $post_type
  */
 function register_post_type( $post_type, $args = array() ) {
 	global $wp_post_types;
diff --git a/src/wp-includes/rest-api.php b/src/wp-includes/rest-api.php
index c1462890213e5..9d6808cd57010 100644
--- a/src/wp-includes/rest-api.php
+++ b/src/wp-includes/rest-api.php
@@ -30,6 +30,9 @@
  * @param bool   $override        Optional. If the route already exists, should we override it? True overrides,
  *                                false merges (with newer overriding if duplicate keys exist). Default false.
  * @return bool True on success, false on error.
+ *
+ * @phpstan-param non-falsy-string $route_namespace
+ * @phpstan-param non-falsy-string $route
  */
 function register_rest_route( $route_namespace, $route, $args = array(), $override = false ) {
 	if ( empty( $route_namespace ) ) {
@@ -694,6 +697,8 @@ function rest_ensure_request( $request ) {
  * @return WP_REST_Response|WP_Error If response generated an error, WP_Error, if response
  *                                   is already an instance, WP_REST_Response, otherwise
  *                                   returns a new WP_REST_Response instance.
+ *
+ * @phpstan-return ($response is WP_Error ? WP_Error : WP_REST_Response)
  */
 function rest_ensure_response( $response ) {
 	if ( is_wp_error( $response ) ) {
@@ -1434,6 +1439,8 @@ function rest_get_date_with_gmt( $date, $is_utc = false ) {
  * @since 4.7.0
  *
  * @return int 401 if the user is not logged in, 403 if the user is logged in.
+ *
+ * @phpstan-return 401|403
  */
 function rest_authorization_required_code() {
 	return is_user_logged_in() ? 403 : 401;
@@ -1531,6 +1538,11 @@ function rest_is_ip_address( $ip ) {
  *
  * @param bool|string|int $value The value being evaluated.
  * @return bool Returns the proper associated boolean value.
+ *
+ * @phpstan-template T of bool|string|int
+ * @phpstan-param T $value
+ * @phpstan-pure
+ * @phpstan-return (T is bool ? T : (T is ''|'false'|'FALSE'|'0'|0 ? false : true))
  */
 function rest_sanitize_boolean( $value ) {
 	// String values are translated to `true`; make sure 'false' is false.
diff --git a/src/wp-includes/revision.php b/src/wp-includes/revision.php
index 6e27fad4fa0a4..499fcc38080d4 100644
--- a/src/wp-includes/revision.php
+++ b/src/wp-includes/revision.php
@@ -18,6 +18,8 @@
  *                                  for insertion as a post revision. Default empty array.
  * @param bool          $deprecated Not used.
  * @return string[] Array of fields that can be versioned.
+ *
+ * @phpstan-param false $deprecated
  */
 function _wp_post_revision_fields( $post = array(), $deprecated = false ) {
 	static $fields = null;
@@ -307,6 +309,12 @@ function wp_get_post_autosave( $post_id, $user_id = 0 ) {
  *
  * @param int|WP_Post $post Post ID or post object.
  * @return int|false ID of revision's parent on success, false if not a revision.
+ *
+ * @phpstan-return (
+ *     $post is WP_Post
+ *         ? false|int<0, max>
+ *         : ($post is int<min, 0> ? false : false|int<0, max>)
+ * )
  */
 function wp_is_post_revision( $post ) {
 	$post = wp_get_post_revision( $post );
diff --git a/src/wp-includes/rewrite.php b/src/wp-includes/rewrite.php
index 976d2a014b9db..0ac4b08f3ffc0 100644
--- a/src/wp-includes/rewrite.php
+++ b/src/wp-includes/rewrite.php
@@ -247,6 +247,9 @@ function remove_permastruct( $name ) {
  * @param string   $feedname Feed name. Should not start with '_'.
  * @param callable $callback Callback to run on feed display.
  * @return string Feed action name.
+ *
+ * @phpstan-param callable(bool, string): void $callback
+ * @phpstan-return non-falsy-string
  */
 function add_feed( $feedname, $callback ) {
 	global $wp_rewrite;
diff --git a/src/wp-includes/robots-template.php b/src/wp-includes/robots-template.php
index e719e745d61e7..14657f74340b0 100644
--- a/src/wp-includes/robots-template.php
+++ b/src/wp-includes/robots-template.php
@@ -66,6 +66,9 @@ function wp_robots() {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_noindex( array $robots ) {
 	if ( ! get_option( 'blog_public' ) ) {
@@ -88,6 +91,9 @@ function wp_robots_noindex( array $robots ) {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_noindex_embeds( array $robots ) {
 	if ( is_embed() ) {
@@ -114,6 +120,9 @@ function wp_robots_noindex_embeds( array $robots ) {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_noindex_search( array $robots ) {
 	if ( is_search() ) {
@@ -136,6 +145,9 @@ function wp_robots_noindex_search( array $robots ) {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_no_robots( array $robots ) {
 	$robots['noindex'] = true;
@@ -163,6 +175,9 @@ function wp_robots_no_robots( array $robots ) {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_sensitive_page( array $robots ) {
 	$robots['noindex']   = true;
@@ -184,6 +199,9 @@ function wp_robots_sensitive_page( array $robots ) {
  *
  * @param array $robots Associative array of robots directives.
  * @return array Filtered robots directives.
+ *
+ * @phpstan-param array<string, bool|string> $robots
+ * @phpstan-return array<string, bool|string>
  */
 function wp_robots_max_image_preview_large( array $robots ) {
 	if ( get_option( 'blog_public' ) ) {
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 7d5ba24e5617d..a8d8afe171b39 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -685,6 +685,8 @@ function wp_default_packages( $scripts ) {
  *
  * @param string $type The type of suffix to retrieve.
  * @return string The script suffix.
+ *
+ * @phpstan-return ''|'.min'
  */
 function wp_scripts_get_suffix( $type = '' ) {
 	static $suffixes;
@@ -2938,6 +2940,9 @@ function wp_enqueue_editor_format_library_assets() {
  *
  * @param array<string, string|bool> $attributes Key-value pairs representing `<script>` tag attributes.
  * @return string String containing `<script>` opening and closing tags.
+ *
+ * @phpstan-param array<string, string|true> $attributes
+ * @phpstan-return non-falsy-string
  */
 function wp_get_script_tag( $attributes ) {
 	/**
@@ -3017,6 +3022,8 @@ function wp_print_script_tag( $attributes ) {
  * @param string                     $data       Data for script tag: JavaScript, importmap, speculationrules, etc.
  * @param array<string, string|bool> $attributes Optional. Key-value pairs representing `<script>` tag attributes.
  * @return string HTML script tag containing the provided $data or the empty string `""` if the data cannot be safely embedded in a script tag.
+ *
+ * @phpstan-param array<string, string|true> $attributes
  */
 function wp_get_inline_script_tag( $data, $attributes = array() ) {
 	$data = "\n" . trim( $data, "\n\r " ) . "\n";
diff --git a/src/wp-includes/shortcodes.php b/src/wp-includes/shortcodes.php
index 01fed7244e548..9f144036d7ed4 100644
--- a/src/wp-includes/shortcodes.php
+++ b/src/wp-includes/shortcodes.php
@@ -59,6 +59,8 @@
  *                           including an array of attributes (`$atts`), the shortcode content
  *                           or null if not set (`$content`), and finally the shortcode tag
  *                           itself (`$shortcode_tag`), in that order.
+ *
+ * @phpstan-param non-empty-string $tag
  */
 function add_shortcode( $tag, $callback ) {
 	global $shortcode_tags;
@@ -129,6 +131,8 @@ function remove_all_shortcodes() {
  *
  * @param string $tag Shortcode tag to check.
  * @return bool Whether the given shortcode exists.
+ *
+ * @phpstan-assert-if-true =non-empty-string $tag
  */
 function shortcode_exists( $tag ) {
 	global $shortcode_tags;
@@ -145,6 +149,10 @@ function shortcode_exists( $tag ) {
  * @param string $content Content to search for shortcodes.
  * @param string $tag     Shortcode tag to check.
  * @return bool Whether the passed content contains the given shortcode.
+ *
+ * @phpstan-assert-if-true =non-falsy-string $content
+ * @phpstan-assert-if-true =non-empty-string $tag
+ * @phpstan-return ($tag is empty ? false : ($content is empty ? false : bool))
  */
 function has_shortcode( $content, $tag ) {
 	if ( ! str_contains( $content, '[' ) ) {
@@ -180,6 +188,8 @@ function has_shortcode( $content, $tag ) {
  *
  * @param string $content The content to check.
  * @return string[] An array of registered shortcode names found in the content.
+ *
+ * @phpstan-return list<non-empty-string>
  */
 function get_shortcode_tags_in_content( $content ) {
 	if ( ! str_contains( $content, '[' ) ) {
@@ -320,6 +330,8 @@ function _filter_do_shortcode_context() {
  *
  * @param array $tagnames Optional. List of shortcodes to find. Defaults to all registered shortcodes.
  * @return string The shortcode search regular expression.
+ *
+ * @phpstan-return non-falsy-string
  */
 function get_shortcode_regex( $tagnames = null ) {
 	global $shortcode_tags;
@@ -589,6 +601,9 @@ function unescape_invalid_shortcodes( $content ) {
  * @since 4.4.0
  *
  * @return string The shortcode attribute regular expression.
+ *
+ * @phpstan-pure
+ * @phpstan-return non-falsy-string
  */
 function get_shortcode_atts_regex() {
 	return '/([\w-]+)\s*=\s*"([^"]*)"(?:\s|$)|([\w-]+)\s*=\s*\'([^\']*)\'(?:\s|$)|([\w-]+)\s*=\s*([^\s\'"]+)(?:\s|$)|"([^"]*)"(?:\s|$)|\'([^\']*)\'(?:\s|$)|(\S+)(?:\s|$)/';
diff --git a/src/wp-includes/taxonomy.php b/src/wp-includes/taxonomy.php
index 6dbc336395f74..aac38e4cbd3a6 100644
--- a/src/wp-includes/taxonomy.php
+++ b/src/wp-includes/taxonomy.php
@@ -374,6 +374,9 @@ function get_taxonomy( $taxonomy ) {
  *
  * @param string $taxonomy Name of taxonomy object.
  * @return bool Whether the taxonomy exists.
+ *
+ * @phpstan-assert-if-true =non-falsy-string $taxonomy
+ * @phpstan-return ($taxonomy is non-falsy-string ? bool : false)
  */
 function taxonomy_exists( $taxonomy ) {
 	global $wp_taxonomies;
@@ -979,6 +982,13 @@ function get_tax_sql( $tax_query, $primary_table, $primary_id_column ) {
  * @param string             $filter   Optional. How to sanitize term fields. Default 'raw'.
  * @return WP_Term|array|WP_Error|null WP_Term instance (or array) on success, depending on the `$output` value.
  *                                     WP_Error if `$taxonomy` does not exist. Null for miscellaneous failure.
+ *
+ * @phpstan-param 'OBJECT'|'ARRAY_A'|'ARRAY_N' $output
+ * @phpstan-return (
+ *     $output is 'ARRAY_A'
+ *         ? array<string, string|int>|WP_Error|null
+ *         : ($output is 'ARRAY_N' ? list<string|int>|WP_Error|null : WP_Term|WP_Error|null)
+ * )
  */
 function get_term( $term, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
 	if ( empty( $term ) ) {
@@ -1101,6 +1111,12 @@ function get_term( $term, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
  * @param string     $filter   Optional. How to sanitize term fields. Default 'raw'.
  * @return WP_Term|array|false WP_Term instance (or array) on success, depending on the `$output` value.
  *                             False if `$taxonomy` does not exist or `$term` was not found.
+ *
+ * @phpstan-return false|(
+ *     $output is 'ARRAY_A'
+ *         ? array<string, string|int>
+ *         : ($output is 'ARRAY_N' ? list<string|int> : WP_Term)
+ * )
  */
 function get_term_by( $field, $value, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
 
@@ -1251,7 +1267,7 @@ function get_term_field( $field, $term, $taxonomy = '', $context = 'display' ) {
  *
  * @param int|object $id       Term ID or object.
  * @param string     $taxonomy Taxonomy name.
- * @return string|int|null|WP_Error Will return empty string if $term is not an object.
+ * @return WP_Term|string|WP_Error Sanitized term, an empty string if `$id` is not a term, or WP_Error on failure.
  */
 function get_term_to_edit( $id, $taxonomy ) {
 	$term = get_term( $id, $taxonomy );
@@ -1756,6 +1772,10 @@ function term_is_ancestor_of( $term1, $term2, $taxonomy ) {
  *                               Accepts 'raw', 'edit', 'db', 'display', 'rss',
  *                               'attribute', or 'js'. Default 'display'.
  * @return array|object Term with all fields sanitized.
+ *
+ * @phpstan-template T of array|object
+ * @phpstan-param T $term
+ * @phpstan-return T
  */
 function sanitize_term( $term, $taxonomy, $context = 'display' ) {
 	$fields = array( 'term_id', 'name', 'description', 'slug', 'count', 'parent', 'term_group', 'term_taxonomy_id', 'object_id' );
@@ -1808,6 +1828,14 @@ function sanitize_term( $term, $taxonomy, $context = 'display' ) {
  *                         Accepts 'raw', 'edit', 'db', 'display', 'rss',
  *                         'attribute', or 'js'.
  * @return mixed Sanitized field.
+ *
+ * @phpstan-template T of string
+ * @phpstan-param T $value
+ * @phpstan-return (
+ *     $field is 'parent'|'term_id'|'count'|'term_group'|'term_taxonomy_id'|'object_id'
+ *         ? int<0, max>
+ *         : ($context is 'raw' ? T : ($context is 'attribute'|'edit'|'js' ? string : mixed))
+ * )
  */
 function sanitize_term_field( $field, $value, $term_id, $taxonomy, $context ) {
 	$int_fields = array( 'parent', 'term_id', 'count', 'term_group', 'term_taxonomy_id', 'object_id' );
@@ -1987,6 +2015,7 @@ function sanitize_term_field( $field, $value, $term_id, $taxonomy, $context ) {
  *                             the integer 0 when the queried parent term is not in the taxonomy
  *                             hierarchy, or WP_Error if the taxonomy does not exist.
  * @phpstan-return numeric-string|0|WP_Error
+ * @phpstan-param '' $deprecated
  */
 function wp_count_terms( $args = array(), $deprecated = '' ) {
 	$use_legacy_args = false;
@@ -2098,7 +2127,7 @@ function wp_delete_term( $term, $taxonomy, $args = array() ) {
 		return $ids;
 	}
 
-	$tt_id = $ids['term_taxonomy_id'];
+	$tt_id = (int) $ids['term_taxonomy_id'];
 
 	$defaults = array();
 
diff --git a/src/wp-includes/user.php b/src/wp-includes/user.php
index 6ce8dbf05175d..eb91e41195b4b 100644
--- a/src/wp-includes/user.php
+++ b/src/wp-includes/user.php
@@ -722,6 +722,8 @@ function count_many_users_posts( $users, $post_type = 'post', $public_only = fal
  * @since MU (3.0.0)
  *
  * @return int The current user's ID, or 0 if no user is logged in.
+ *
+ * @phpstan-return int<0, max>
  */
 function get_current_user_id() {
 	if ( ! function_exists( 'wp_get_current_user' ) ) {
@@ -749,6 +751,8 @@ function get_current_user_id() {
  * @param int    $user       Optional. User ID.
  * @param string $deprecated Use get_option() to check for an option in the options table.
  * @return mixed User option value on success, false on failure.
+ *
+ * @phpstan-param '' $deprecated
  */
 function get_user_option( $option, $user = 0, $deprecated = '' ) {
 	global $wpdb;
@@ -854,6 +858,8 @@ function delete_user_option( $user_id, $option_name, $is_global = false ) {
  *
  * @param int $user_id User ID.
  * @return WP_User|false WP_User object on success, false on failure.
+ *
+ * @phpstan-return ($user_id is int<min, 0> ? false : WP_User|false)
  */
 function get_user( $user_id ) {
 	return get_user_by( 'id', $user_id );
@@ -3101,6 +3107,8 @@ function wp_get_password_hint() {
  *
  * @param WP_User $user User to retrieve password reset key for.
  * @return string|WP_Error Password reset key on success. WP_Error on error.
+ *
+ * @phpstan-impure
  */
 function get_password_reset_key( $user ) {
 	if ( ! ( $user instanceof WP_User ) ) {
diff --git a/src/wp-includes/widgets.php b/src/wp-includes/widgets.php
index 7661e6d3f45fc..67ba8ec3b744a 100644
--- a/src/wp-includes/widgets.php
+++ b/src/wp-includes/widgets.php
@@ -116,6 +116,9 @@
  * @global WP_Widget_Factory $wp_widget_factory
  *
  * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
+ *
+ * @phpstan-param class-string<WP_Widget>|WP_Widget $widget
+ * @phpstan-return void
  */
 function register_widget( $widget ) {
 	global $wp_widget_factory;
@@ -1017,6 +1020,8 @@ function is_active_sidebar( $index ) {
  *
  * @param bool $deprecated Not used (argument deprecated).
  * @return array Upgraded list of widgets to version 3 array format when called from the admin.
+ *
+ * @phpstan-param true $deprecated
  */
 function wp_get_sidebars_widgets( $deprecated = true ) {
 	if ( true !== $deprecated ) {
@@ -1708,6 +1713,26 @@ function wp_widget_rss_output( $rss, $args = array() ) {
  *
  * @param array|string $args   Values for input fields.
  * @param array        $inputs Override default display options.
+ *
+ * @phpstan-param array{
+ *     number: int,
+ *     error: string|false,
+ *     title?: string,
+ *     url?: string,
+ *     items?: int,
+ *     show_summary?: int,
+ *     show_author?: int,
+ *     show_date?: int,
+ * } $args
+ * @phpstan-param array{
+ *     title?: bool,
+ *     url?: bool,
+ *     items?: bool,
+ *     show_summary?: bool,
+ *     show_author?: bool,
+ *     show_date?: bool,
+ * } $inputs
+ * @phpstan-return void
  */
 function wp_widget_rss_form( $args, $inputs = null ) {
 	$default_inputs = array(
@@ -1793,6 +1818,17 @@ function wp_widget_rss_form( $args, $inputs = null ) {
  * @param array $widget_rss RSS widget feed data. Expects unescaped data.
  * @param bool  $check_feed Optional. Whether to check feed for errors. Default true.
  * @return array
+ *
+ * @phpstan-return array{
+ *     title: string,
+ *     url: string,
+ *     link: string,
+ *     items: int<1, 20>,
+ *     error: string|false,
+ *     show_summary: int,
+ *     show_author: int,
+ *     show_date: int,
+ * }
  */
 function wp_widget_rss_process( $widget_rss, $check_feed = true ) {
 	$items = (int) $widget_rss['items'];
diff --git a/tests/phpstan/README.md b/tests/phpstan/README.md
index 3ab750a069471..6dc5935f2c2e8 100644
--- a/tests/phpstan/README.md
+++ b/tests/phpstan/README.md
@@ -106,6 +106,17 @@ Calls whose hook name contains no literal text, such as the `apply_filters_ref_a
 
 One consequence worth knowing: because a hook's documentation may live in a different file than the call inheriting it, editing a hook docblock in a file that reference comments point at discards PHPStan's result cache. Every call site inheriting that docblock has to be analyzed again, and PHPStan cannot infer that dependency on its own.
 
+### Extensions from szepeviktor/phpstan-wordpress
+
+[szepeviktor/phpstan-wordpress](https://github.com/szepeviktor/phpstan-wordpress) is the set of PHPStan extensions maintained for the WordPress ecosystem, and the hook extensions above began as adaptations of it. It is installed as a Composer development dependency so that core can load its extensions directly rather than carry copies of them. Its own `extension.neon` is not included, because that loads [php-stubs/wordpress-stubs](https://github.com/php-stubs/wordpress-stubs), a declaration of every core function and class, which is the code being analyzed here. Instead, [`base.neon`](base.neon) registers the extensions that apply to core one at a time. Installing the package installs the stubs as well; they are not read.
+
+What the package provides falls into four groups, and only the first is loaded:
+
+- **Used, because a docblock cannot express what they do.** `ShortcodeAttsDynamicFunctionReturnTypeExtension` types the result of `shortcode_atts()` from the defaults passed to it, the same merge that `wp_parse_args()` performs. `HookCallbackRule` checks a callback registered with `add_action()` or `add_filter()` against its registration: that `$accepted_args` agrees with the parameters the callback declares, and that a filter callback returns a value. Its third check, that an action callback returns nothing, does not fit core, which registers functions that happen to return a value on actions as a matter of course and discards the value; each such registration carries an inline `@phpstan-ignore` saying so. `HookDocsRule` checks that the type each `@param` of a hook docblock documents accepts the value the hook passes. That documented type is what `apply_filters()` is typed from, so a wrong one misleads every caller. It reads only a docblock written at the call, so a hook documented elsewhere through a reference comment is not checked.
+- **Not used, because core's own versions do the same and more.** `HookDocsVisitor`, `HookDocBlock` and `ApplyFiltersDynamicFunctionReturnTypeExtension` are what the [hook documentation](#hook-documentation) extensions were adapted from. Core's resolve the "This filter is documented in" reference comments, which the originals do not, and core's rules already check the `@param` counts that `HookDocsRule` also checks, so only its type check adds anything.
+- **Not used, because a docblock does the same.** `EscSql`, `NormalizeWhitespace`, `StripslashesFromStringsOnly`, `SlashitFunctions`, `WpParseUrl` and `WpSlash` each narrow one function's return type from its arguments in a way a conditional `@phpstan-return` expresses. Where core has that docblock already, as `wp_parse_url()`, `wp_slash()` and `stripslashes_from_strings_only()` do, loading the extension changes nothing; where it does not yet, as `esc_sql()`, the docblock is the fix to make. A docblock in core also types the function for every plugin, since the stubs are generated from core. phpstan-wordpress itself has gone that way: its 2.x branch dropped the extensions it had for `get_post()`, `get_terms()`, `current_time()`, `wp_die()`, `is_wp_error()` and others in favor of types carried by the stubs. The [function map](https://github.com/php-stubs/wordpress-stubs/blob/master/functionMap.php) those stubs applied on top of core's docblocks has since been brought into core itself, as `@phpstan-param` and `@phpstan-return` tags on the functions it named, so the same types now reach core's own analysis, the stubs, and every plugin from one place.
+- **Not applicable to core.** `WpConstantFetchRule` discourages reading a constant such as `MULTISITE` where a function exists to read it, but core is where those functions read them. `AssertWpErrorTypeSpecifyingExtension` narrows the argument of `assertWPError()` in tests, which are not analyzed; when they are, `@phpstan-assert` on the methods themselves is the way to express it.
+
 ### Errors these rules report
 
 These identifiers are specific to WordPress, and can be ignored or baselined like any other error, as described [below](#ignoring-and-baselining-errors).
@@ -118,6 +129,17 @@ These identifiers are specific to WordPress, and can be ignored or baselined lik
 | `wordpress.hookDocReferenceHookMissing` | The referenced file exists, but documents no hook of that name. Either the reference is stale, or the canonical docblock has moved. |
 | `wordpress.hookParamCountMismatch` | The call passes a different number of arguments than the docblock documents `@param` tags for. Passing fewer risks an `ArgumentCountError` in a callback registered for the documented count; passing more silently drops the extra argument and leaves the documentation misleading. |
 
+The rules loaded from szepeviktor/phpstan-wordpress report under PHPStan's own identifiers rather than ones of their own, so their errors share a baseline with the errors PHPStan itself reports under that identifier. They are told apart by their messages.
+
+| Identifier | Message | What it means |
+| --- | --- | --- |
+| `arguments.count` | `Callback expects N parameters, $accepted_args is set to M.` | The `$accepted_args` of an `add_action()` or `add_filter()` call does not fit the callback's signature. Fewer than the callback requires is an `ArgumentCountError` when the hook fires; more than it declares is misleading, and usually a leftover from an earlier signature. |
+| `return.missing` | `Filter callback return statement is missing.` | A filter callback returns nothing, so the value being filtered becomes `null`. |
+| `return.void` | `Action callback returns X but should not return anything.` | An action callback returns a value. WordPress discards it, so where core registers such a function deliberately the call carries an inline `@phpstan-ignore` saying so. |
+| `parameter.phpDocType` | `@param X $name does not accept actual type of parameter: Y.` | The type a hook docblock documents for a parameter does not accept the value the hook passes. Fix the docblock, or the value; the documented type is what callbacks and the `apply_filters()` return type rely on. |
+| `paramTag.count` | `Expected N @param tags, found M.` | The same mismatch `wordpress.hookParamCountMismatch` reports, for a docblock written at the call. |
+| `phpDoc.parseError` | `One or more @param tags has an invalid name or invalid syntax.` | A `@param` tag in a hook docblock could not be parsed, or is named `$this`. |
+
 ## Ignoring and baselining errors
 
 As we adopt PHPStan iteratively, you may be faced with false positives due to legacy code, or code that is not worth changing at this time.
diff --git a/tests/phpstan/base.neon b/tests/phpstan/base.neon
index 4cf457f07e0f7..f7a5ad88bc4f2 100644
--- a/tests/phpstan/base.neon
+++ b/tests/phpstan/base.neon
@@ -62,6 +62,42 @@ services:
 		tags:
 			- phpstan.resultCacheMetaExtension
 
+	# The services below come from szepeviktor/phpstan-wordpress, the PHPStan extensions
+	# maintained for the WordPress ecosystem, installed through Composer. Its own
+	# extension.neon is deliberately not included: that bootstraps php-stubs/wordpress-stubs,
+	# which describes the very code analyzed here, so every function and class would be
+	# declared twice. Instead, the extensions that apply to core are registered one by one.
+	# See tests/phpstan/README.md for which ones are used, which are not, and why.
+
+	# Types the return value of shortcode_atts() from the defaults it was called with, so
+	# a shortcode's attributes are an array shape rather than a plain array. The merge
+	# a call performs is not something a docblock can express.
+	-
+		class: SzepeViktor\PHPStan\WordPress\ShortcodeAttsDynamicFunctionReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicFunctionReturnTypeExtension
+
+	# Checks the callback given to add_action() and add_filter() against the call: that
+	# `$accepted_args` agrees with the number of parameters the callback declares, that
+	# a filter callback returns a value, and that an action callback does not. The last
+	# check is switched off for core in phpstan.neon.dist; see the note there.
+	-
+		class: SzepeViktor\PHPStan\WordPress\HookCallbackRule
+		tags:
+			- phpstan.rules.rule
+
+	# Checks that the type each `@param` of a hook docblock documents accepts the value
+	# the hook passes. That documented type is what apply_filters() is typed from above,
+	# so a wrong one misleads every caller. Only a docblock written at the call is checked:
+	# the rule reads the docblock through phpstan-wordpress's own resolver, registered
+	# beside it, which does not follow "This filter is documented in" reference comments.
+	-
+		class: SzepeViktor\PHPStan\WordPress\HookDocBlock
+	-
+		class: SzepeViktor\PHPStan\WordPress\HookDocsRule
+		tags:
+			- phpstan.rules.rule
+
 	# Runs the visitors above over every file PHPStan parses, not only the ones it
 	# analyzes.
 	#
diff --git a/tests/phpstan/baselines/argument.type.neon b/tests/phpstan/baselines/argument.type.neon
index 14681f13d929a..2fad06acde104 100644
--- a/tests/phpstan/baselines/argument.type.neon
+++ b/tests/phpstan/baselines/argument.type.neon
@@ -318,11 +318,6 @@ parameters:
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-admin/includes/upgrade.php
-		-
-			message: '#^Parameter \#3 \$deprecated of function add_option expects string, null given\.$#'
-			identifier: argument.type
-			count: 1
-			path: ../../../src/wp-admin/includes/upgrade.php
 		-
 			message: '#^Parameter \#1 \$bookmark_id of function clean_bookmark_cache expects int, string\|null given\.$#'
 			identifier: argument.type
@@ -729,7 +724,7 @@ parameters:
 			count: 1
 			path: ../../../src/wp-includes/class-wp-customize-manager.php
 		-
-			message: '#^Parameter \#1 \$postarr of function wp_insert_post expects array\{ID\?\: int, post_author\?\: int, post_date\?\: string, post_date_gmt\?\: string, post_content\?\: string, post_content_filtered\?\: string, post_title\?\: string, post_excerpt\?\: string, \.\.\., \.\.\.\}, array\<int\|string\|false\> given\.$#'
+			message: '#^Parameter \#1 \$postarr of function wp_insert_post expects array\{ID\?\: int, post_author\?\: int, post_date\?\: string, post_date_gmt\?\: string, post_content\?\: string, post_content_filtered\?\: string, post_title\?\: string, post_excerpt\?\: string, \.\.\., \.\.\.\}, array\<int\<min, \-1\>\|int\<1, max\>\|string\|false\> given\.$#'
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-includes/class-wp-customize-manager.php
@@ -844,12 +839,12 @@ parameters:
 			count: 1
 			path: ../../../src/wp-includes/class-wp-user.php
 		-
-			message: '#^Parameter \#1 \$number of method WP_Widget\:\:_set\(\) expects int, string given\.$#'
+			message: '#^Parameter \#1 \$number of method WP_Widget\<T of array \= array\<string, mixed\>\>\:\:_set\(\) expects int, string given\.$#'
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-includes/class-wp-widget.php
 		-
-			message: '#^Parameter \#1 \$postarr of function wp_insert_post expects array\{ID\?\: int, post_author\?\: int, post_date\?\: string, post_date_gmt\?\: string, post_content\?\: string, post_content_filtered\?\: string, post_title\?\: string, post_excerpt\?\: string, \.\.\., \.\.\.\}, array\{post_author\: int, post_date\: int\|string, post_date_gmt\: int\|string, post_content\: string, post_title\: string, post_category\: array\<string\>\|string, post_status\: ''draft''\|''publish''\} given\.$#'
+			message: '#^Parameter \#1 \$postarr of function wp_insert_post expects array\{ID\?\: int, post_author\?\: int, post_date\?\: string, post_date_gmt\?\: string, post_content\?\: string, post_content_filtered\?\: string, post_title\?\: string, post_excerpt\?\: string, \.\.\., \.\.\.\}, array\{post_author\: int, post_date\: string, post_date_gmt\: string, post_content\: string, post_title\: string, post_category\: array\<string\>\|string, post_status\: ''draft''\|''publish''\} given\.$#'
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-includes/class-wp-xmlrpc-server.php
@@ -1039,7 +1034,7 @@ parameters:
 			count: 1
 			path: ../../../src/wp-includes/load.php
 		-
-			message: '#^Parameter \#5 \$text of function wp_get_attachment_link expects string\|false, bool given\.$#'
+			message: '#^Parameter \#1 \$args of function get_posts expects array\{numberposts\?\: int, category\?\: int\|string, include\?\: array\<int\>, exclude\?\: array\<int\>, suppress_filters\?\: bool, \.\.\.\}\|string\|null, array\{include\: non\-falsy\-string, post_status\: ''inherit'', post_type\: ''attachment'', post_mime_type\: ''image'', order\: string, orderby\: string\} given\.$#'
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-includes/media.php
diff --git a/tests/phpstan/baselines/arguments.count.neon b/tests/phpstan/baselines/arguments.count.neon
index e3cab51b3621e..8a754d7469c7e 100644
--- a/tests/phpstan/baselines/arguments.count.neon
+++ b/tests/phpstan/baselines/arguments.count.neon
@@ -18,21 +18,6 @@
 
 parameters:
 	ignoreErrors:
-		-
-			message: '#^Method WP_List_Table\:\:display_rows\(\) invoked with 2 parameters, 0 required\.$#'
-			identifier: arguments.count
-			count: 1
-			path: ../../../src/wp-admin/includes/ajax-actions.php
-		-
-			message: '#^Method WP_List_Table\:\:single_row\(\) invoked with 2 parameters, 1 required\.$#'
-			identifier: arguments.count
-			count: 2
-			path: ../../../src/wp-admin/includes/ajax-actions.php
-		-
-			message: '#^Method WP_List_Table\:\:single_row\(\) invoked with 3 parameters, 1 required\.$#'
-			identifier: arguments.count
-			count: 1
-			path: ../../../src/wp-admin/includes/ajax-actions.php
 		-
 			message: '#^Method WP_Upgrader_Skin\:\:before\(\) invoked with 1 parameter, 0 required\.$#'
 			identifier: arguments.count
@@ -43,8 +28,3 @@ parameters:
 			identifier: arguments.count
 			count: 2
 			path: ../../../src/wp-admin/includes/class-theme-upgrader.php
-		-
-			message: '#^Method WP_List_Table\:\:display\(\) invoked with 1 parameter, 0 required\.$#'
-			identifier: arguments.count
-			count: 1
-			path: ../../../src/wp-admin/includes/meta-boxes.php
diff --git a/tests/phpstan/baselines/deadCode.unreachable.neon b/tests/phpstan/baselines/deadCode.unreachable.neon
index 8a4288bc40c43..9c8bebbc5db27 100644
--- a/tests/phpstan/baselines/deadCode.unreachable.neon
+++ b/tests/phpstan/baselines/deadCode.unreachable.neon
@@ -31,7 +31,7 @@ parameters:
 		-
 			message: '#^Unreachable statement \- code above always terminates\.$#'
 			identifier: deadCode.unreachable
-			count: 3
+			count: 2
 			path: ../../../src/wp-admin/includes/ajax-actions.php
 		-
 			message: '#^Unreachable statement \- code above always terminates\.$#'
diff --git a/tests/phpstan/baselines/if.alwaysFalse.neon b/tests/phpstan/baselines/if.alwaysFalse.neon
index 6e33ed2a5365c..cc72813ceafbc 100644
--- a/tests/phpstan/baselines/if.alwaysFalse.neon
+++ b/tests/phpstan/baselines/if.alwaysFalse.neon
@@ -28,11 +28,6 @@ parameters:
 			identifier: if.alwaysFalse
 			count: 2
 			path: ../../../src/wp-includes/class-wp-block-processor.php
-		-
-			message: '#^If condition is always false\.$#'
-			identifier: if.alwaysFalse
-			count: 1
-			path: ../../../src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
 		-
 			message: '#^If condition is always false\.$#'
 			identifier: if.alwaysFalse
diff --git a/tests/phpstan/baselines/isset.property.neon b/tests/phpstan/baselines/isset.property.neon
index ab7d839e22002..fa7b3d126e71d 100644
--- a/tests/phpstan/baselines/isset.property.neon
+++ b/tests/phpstan/baselines/isset.property.neon
@@ -144,7 +144,7 @@ parameters:
 			count: 1
 			path: ../../../src/wp-includes/class-wp-user.php
 		-
-			message: '#^Property WP_Widget\:\:\$alt_option_name \(string\) in isset\(\) is not nullable\.$#'
+			message: '#^Property WP_Widget\<T of array \= array\<string, mixed\>\>\:\:\$alt_option_name \(string\) in isset\(\) is not nullable\.$#'
 			identifier: isset.property
 			count: 1
 			path: ../../../src/wp-includes/class-wp-widget.php
@@ -186,7 +186,7 @@ parameters:
 		-
 			message: '#^Property WP_Term\:\:\$term_id \(int\) in isset\(\) is not nullable\.$#'
 			identifier: isset.property
-			count: 1
+			count: 2
 			path: ../../../src/wp-includes/nav-menu.php
 		-
 			message: '#^Property WP_Post\:\:\$post_name \(string\) in isset\(\) is not nullable\.$#'
diff --git a/tests/phpstan/baselines/method.nonObject.neon b/tests/phpstan/baselines/method.nonObject.neon
deleted file mode 100644
index 4d0727f8950f1..0000000000000
--- a/tests/phpstan/baselines/method.nonObject.neon
+++ /dev/null
@@ -1,55 +0,0 @@
-# PHPStan baseline for the `method.nonObject` errors in WordPress core.
-#
-# https://phpstan.org/error-identifiers/method.nonObject
-#
-# Each entry is scoped to a single file and carries an exact occurrence count,
-# so that a new instance is reported as a new error rather than being absorbed
-# silently. Fixing an occurrence therefore means decrementing or removing its
-# entry here as part of the same change.
-#
-# The goal is to empty this file and delete it, along with the `includes` entry
-# for it in phpstan.neon.dist.
-#
-# Generated by `composer phpstan:baselines`. Do not edit by hand; regenerate with
-#
-#     composer phpstan:baselines -- --identifier=method.nonObject
-#
-# which reruns the analysis with this file suppressed so the errors surface again.
-
-parameters:
-	ignoreErrors:
-		-
-			message: '#^Cannot call method inline_edit\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/edit-tags.php
-		-
-			message: '#^Cannot call method inline_edit\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/edit.php
-		-
-			message: '#^Cannot call method embed_scripts\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/erase-personal-data.php
-		-
-			message: '#^Cannot call method process_bulk_action\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/erase-personal-data.php
-		-
-			message: '#^Cannot call method embed_scripts\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/export-personal-data.php
-		-
-			message: '#^Cannot call method process_bulk_action\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/export-personal-data.php
-		-
-			message: '#^Cannot call method theme_installer_single\(\) on WP_List_Table\|false\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: ../../../src/wp-admin/includes/theme-install.php
diff --git a/tests/phpstan/baselines/parameter.defaultValue.neon b/tests/phpstan/baselines/parameter.defaultValue.neon
deleted file mode 100644
index 34b6b678fc447..0000000000000
--- a/tests/phpstan/baselines/parameter.defaultValue.neon
+++ /dev/null
@@ -1,105 +0,0 @@
-# PHPStan baseline for the `parameter.defaultValue` errors in WordPress core.
-#
-# https://phpstan.org/error-identifiers/parameter.defaultValue
-#
-# Each entry is scoped to a single file and carries an exact occurrence count,
-# so that a new instance is reported as a new error rather than being absorbed
-# silently. Fixing an occurrence therefore means decrementing or removing its
-# entry here as part of the same change.
-#
-# The goal is to empty this file and delete it, along with the `includes` entry
-# for it in phpstan.neon.dist.
-#
-# Generated by `composer phpstan:baselines`. Do not edit by hand; regenerate with
-#
-#     composer phpstan:baselines -- --identifier=parameter.defaultValue
-#
-# which reruns the analysis with this file suppressed so the errors surface again.
-
-parameters:
-	ignoreErrors:
-		-
-			message: '#^Default value of the parameter \#1 \$admin_header_callback \(''''\) of method Custom_Background\:\:__construct\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/class-custom-background.php
-		-
-			message: '#^Default value of the parameter \#2 \$admin_image_div_callback \(''''\) of method Custom_Background\:\:__construct\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/class-custom-background.php
-		-
-			message: '#^Default value of the parameter \#2 \$admin_image_div_callback \(''''\) of method Custom_Image_Header\:\:__construct\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/class-custom-image-header.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_comments_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_dashboard_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_links_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_management_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_media_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_menu_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_options_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_pages_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_plugins_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_posts_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_theme_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#5 \$callback \(''''\) of function add_users_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#6 \$callback \(''''\) of function add_submenu_page\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-admin/includes/plugin.php
-		-
-			message: '#^Default value of the parameter \#3 \$deprecated \(''''\) of function unregister_setting\(\) is incompatible with type callable\(\)\: mixed\.$#'
-			identifier: parameter.defaultValue
-			count: 1
-			path: ../../../src/wp-includes/option.php
diff --git a/tests/phpstan/baselines/property.nonObject.neon b/tests/phpstan/baselines/property.nonObject.neon
index d242b9373685b..4c8e2bfea6150 100644
--- a/tests/phpstan/baselines/property.nonObject.neon
+++ b/tests/phpstan/baselines/property.nonObject.neon
@@ -73,16 +73,6 @@ parameters:
 			identifier: property.nonObject
 			count: 1
 			path: ../../../src/wp-admin/includes/class-wp-plugin-install-list-table.php
-		-
-			message: '#^Cannot access property \$parent on array\|object\.$#'
-			identifier: property.nonObject
-			count: 1
-			path: ../../../src/wp-admin/includes/class-wp-terms-list-table.php
-		-
-			message: '#^Cannot access property \$term_id on array\|object\.$#'
-			identifier: property.nonObject
-			count: 2
-			path: ../../../src/wp-admin/includes/class-wp-terms-list-table.php
 		-
 			message: '#^Cannot access property \$info on array\|object\.$#'
 			identifier: property.nonObject
@@ -183,21 +173,11 @@ parameters:
 			identifier: property.nonObject
 			count: 1
 			path: ../../../src/wp-includes/class-wp-customize-manager.php
-		-
-			message: '#^Cannot access property \$object_id on array\|WP_Error\|WP_Term\.$#'
-			identifier: property.nonObject
-			count: 1
-			path: ../../../src/wp-includes/class-wp-term-query.php
 		-
 			message: '#^Cannot access property \$term_id on string\|WP_Customize_Setting\.$#'
 			identifier: property.nonObject
 			count: 1
 			path: ../../../src/wp-includes/customize/class-wp-customize-nav-menu-control.php
-		-
-			message: '#^Cannot access property \$link_id on array\|object\.$#'
-			identifier: property.nonObject
-			count: 3
-			path: ../../../src/wp-includes/link-template.php
 		-
 			message: '#^Cannot access property \$plugins on array\|object\.$#'
 			identifier: property.nonObject
@@ -218,18 +198,8 @@ parameters:
 			identifier: property.nonObject
 			count: 1
 			path: ../../../src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
-		-
-			message: '#^Cannot access property \$parent on array\|object\.$#'
-			identifier: property.nonObject
-			count: 1
-			path: ../../../src/wp-includes/taxonomy.php
 		-
 			message: '#^Cannot access property \$template_name on array\.$#'
 			identifier: property.nonObject
 			count: 1
 			path: ../../../src/wp-includes/taxonomy.php
-		-
-			message: '#^Cannot access property \$term_id on array\|object\.$#'
-			identifier: property.nonObject
-			count: 4
-			path: ../../../src/wp-includes/taxonomy.php
diff --git a/tests/phpstan/baselines/property.notFound.neon b/tests/phpstan/baselines/property.notFound.neon
index c7d60d13061d2..521bc7619766a 100644
--- a/tests/phpstan/baselines/property.notFound.neon
+++ b/tests/phpstan/baselines/property.notFound.neon
@@ -158,26 +158,6 @@ parameters:
 			identifier: property.notFound
 			count: 1
 			path: ../../../src/wp-admin/includes/class-walker-nav-menu-edit.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$author\.$#'
-			identifier: property.notFound
-			count: 3
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$name\.$#'
-			identifier: property.notFound
-			count: 4
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$parent_theme\.$#'
-			identifier: property.notFound
-			count: 1
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$version\.$#'
-			identifier: property.notFound
-			count: 6
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
 		-
 			message: '#^Access to an undefined property WP_Theme\:\:\$auto_update_forced\.$#'
 			identifier: property.notFound
@@ -188,11 +168,6 @@ parameters:
 			identifier: property.notFound
 			count: 1
 			path: ../../../src/wp-admin/includes/class-wp-ms-themes-list-table.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$name\.$#'
-			identifier: property.notFound
-			count: 8
-			path: ../../../src/wp-admin/includes/class-wp-site-health.php
 		-
 			message: '#^Access to an undefined property WP_Post\:\:\$_wp_attachment_image_alt\.$#'
 			identifier: property.notFound
@@ -228,11 +203,6 @@ parameters:
 			identifier: property.notFound
 			count: 2
 			path: ../../../src/wp-admin/nav-menus.php
-		-
-			message: '#^Access to an undefined property WP_Theme\:\:\$version\.$#'
-			identifier: property.notFound
-			count: 1
-			path: ../../../src/wp-admin/update-core.php
 		-
 			message: '#^Access to an undefined property WP_Post\:\:\$description\.$#'
 			identifier: property.notFound
@@ -293,6 +263,11 @@ parameters:
 			identifier: property.notFound
 			count: 2
 			path: ../../../src/wp-includes/class-walker-nav-menu.php
+		-
+			message: '#^Access to an undefined property WP_Error\|WP_Term\:\:\$object_id\.$#'
+			identifier: property.notFound
+			count: 1
+			path: ../../../src/wp-includes/class-wp-term-query.php
 		-
 			message: '#^Access to an undefined property WP_Query\:\:\$comments_by_type\.$#'
 			identifier: property.notFound
diff --git a/tests/phpstan/baselines/property.private.neon b/tests/phpstan/baselines/property.private.neon
index 900a8e51dc423..7549ab9c5ddd5 100644
--- a/tests/phpstan/baselines/property.private.neon
+++ b/tests/phpstan/baselines/property.private.neon
@@ -18,16 +18,6 @@
 
 parameters:
 	ignoreErrors:
-		-
-			message: '#^Access to private property WP_Theme\:\:\$stylesheet\.$#'
-			identifier: property.private
-			count: 20
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
-		-
-			message: '#^Access to private property WP_Theme\:\:\$template\.$#'
-			identifier: property.private
-			count: 2
-			path: ../../../src/wp-admin/includes/class-wp-debug-data.php
 		-
 			message: '#^Access to private property WP_Block_Type\:\:\$uses_context\.$#'
 			identifier: property.private
diff --git a/tests/phpstan/baselines/property.protected.neon b/tests/phpstan/baselines/property.protected.neon
index b29d125bd2a7a..43fe90c187140 100644
--- a/tests/phpstan/baselines/property.protected.neon
+++ b/tests/phpstan/baselines/property.protected.neon
@@ -19,17 +19,17 @@
 parameters:
 	ignoreErrors:
 		-
-			message: '#^Access to protected property WP_List_Table\:\:\$screen\.$#'
+			message: '#^Access to protected property WP_Privacy_Data_Removal_Requests_List_Table\:\:\$screen\.$#'
 			identifier: property.protected
 			count: 1
 			path: ../../../src/wp-admin/erase-personal-data.php
 		-
-			message: '#^Access to protected property WP_List_Table\:\:\$screen\.$#'
+			message: '#^Access to protected property WP_Privacy_Data_Export_Requests_List_Table\:\:\$screen\.$#'
 			identifier: property.protected
 			count: 1
 			path: ../../../src/wp-admin/export-personal-data.php
 		-
-			message: '#^Access to protected property WP_List_Table\:\:\$screen\.$#'
+			message: '#^Access to protected property WP_Posts_List_Table\:\:\$screen\.$#'
 			identifier: property.protected
 			count: 1
 			path: ../../../src/wp-admin/includes/ajax-actions.php
diff --git a/tests/phpstan/baselines/return.unusedType.neon b/tests/phpstan/baselines/return.unusedType.neon
index 2acebf529a781..a1a27541a6f7c 100644
--- a/tests/phpstan/baselines/return.unusedType.neon
+++ b/tests/phpstan/baselines/return.unusedType.neon
@@ -78,16 +78,6 @@ parameters:
 			identifier: return.unusedType
 			count: 1
 			path: ../../../src/wp-includes/revision.php
-		-
-			message: '#^Function get_term_to_edit\(\) never returns int so it can be removed from the return type\.$#'
-			identifier: return.unusedType
-			count: 1
-			path: ../../../src/wp-includes/taxonomy.php
-		-
-			message: '#^Function get_term_to_edit\(\) never returns null so it can be removed from the return type\.$#'
-			identifier: return.unusedType
-			count: 1
-			path: ../../../src/wp-includes/taxonomy.php
 		-
 			message: '#^Function wp_is_password_reset_allowed_for_user\(\) never returns WP_Error so it can be removed from the return type\.$#'
 			identifier: return.unusedType