diff --git a/.distignore b/.distignore
index 022e7a7..10440b1 100644
--- a/.distignore
+++ b/.distignore
@@ -15,4 +15,5 @@
 /package.json
 /package-lock.json
 /phpcs.xml
+/phpstan.neon
 /phpunit.xml
diff --git a/.gitattributes b/.gitattributes
index d0f8b5b..ad1e8ff 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -11,4 +11,5 @@ composer.lock export-ignore
 CONTRIBUTING.md export-ignore
 package.json export-ignore
 phpcs.xml export-ignore
+phpstan.neon export-ignore
 phpunit.xml export-ignore
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 949a72c..55b43bc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,10 +5,10 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: [ '5.6', '7.4', '8.0', '8.2', '8.4' ]
+        php: [ '7.4', '8.0', '8.2', '8.4', '8.5' ]
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup PHP
@@ -25,7 +25,7 @@ jobs:
           sed -i "s#<file name=\"${GITHUB_WORKSPACE}#<file name=\"/github/workspace#g" tests-clover.xml
       - name: Analyze with SonarCloud
         if: matrix.php == '8.2' && env.SONAR_TOKEN != ''
-        uses: sonarsource/sonarcloud-github-action@master
+        uses: sonarsource/sonarqube-scan-action@v6
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
@@ -43,7 +43,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
@@ -53,3 +53,20 @@ jobs:
         run: composer install --no-interaction
       - name: Code style checks for PHP
         run: composer test-cs
+
+  phpstan:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.4
+          tools: composer
+      - name: Install PHP dependencies
+        run: composer install --no-interaction --prefer-dist --no-scripts
+      - name: PHPStan
+        run: composer phpstan
diff --git a/.github/workflows/wordpress-plugin-asset-update.yml b/.github/workflows/wordpress-plugin-asset-update.yml
index f848c9a..55aade1 100644
--- a/.github/workflows/wordpress-plugin-asset-update.yml
+++ b/.github/workflows/wordpress-plugin-asset-update.yml
@@ -8,7 +8,7 @@ jobs:
     name: Push to stable
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Clean README.md
         run: tail -n +6 README.md > README.md.tmp && mv README.md.tmp README.md
       - name: WordPress.org plugin asset/readme update
diff --git a/.github/workflows/wordpress-plugin-check.yml b/.github/workflows/wordpress-plugin-check.yml
index a5596c0..aa9f8dd 100644
--- a/.github/workflows/wordpress-plugin-check.yml
+++ b/.github/workflows/wordpress-plugin-check.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Package plugin
         run: |
diff --git a/.github/workflows/wordpress-plugin-deploy.yml b/.github/workflows/wordpress-plugin-deploy.yml
index b8395bc..a95eb20 100644
--- a/.github/workflows/wordpress-plugin-deploy.yml
+++ b/.github/workflows/wordpress-plugin-deploy.yml
@@ -9,7 +9,7 @@ jobs:
     name: New tag
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Clean README.md
         run: tail -n +6 README.md > README.md.tmp && mv README.md.tmp README.md
       - name: WordPress Plugin Deploy
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8e24a86..56017dd 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -110,7 +110,7 @@ The coverage is not yet perfect, but be invited to write tests for methods not y
 This project, as part of the WordPress ecosystem adheres to the [WordPress Coding Standards](https://codex.wordpress.org/WordPress_Coding_Standards).
 Please make sure that you are at least roughly familiar with those guidelines.
 
-The code style is automatically checked for commits (including pull requests) using [PHP CodeSniffer](https://github.com/squizlabs/PHP_CodeSniffer).
+The code style is automatically checked for commits (including pull requests) using [PHP CodeSniffer](https://github.com/PHPCSStandards/PHP_CodeSniffer).
 You can check your code against the configured ruleset yourself by running
  `./vendor/bin/phpcs --standard=phpcs.xml your-edited-file.php` (assuming `composer install` has been executed) or the Robo task `robo test:cs` for a complete scan.
 
diff --git a/README.md b/README.md
index 5e9773b..67856c6 100644
--- a/README.md
+++ b/README.md
@@ -5,10 +5,10 @@
 
 # Statify Filter #
 * Contributors:      stklcode
-* Requires at least: 4.7
-* Tested up to:      6.8
-* Requires PHP:      5.5
-* Stable tag:        1.7.2
+* Requires at least: 5.1
+* Tested up to:      7.0
+* Requires PHP:      7.4
+* Stable tag:        1.8.0
 * License:           GPLv2 or later
 * License URI:       https://www.gnu.org/licenses/gpl-2.0.html
 
@@ -55,8 +55,8 @@ The plugin is capable of handling multisite installations.
 * Goto _Settings_ -> _Statify Filter_ to configure the plugin
 
 ### Requirements ###
-* PHP 5.5 or above
-* WordPress 4.7 or above
+* PHP 7.4 or above
+* WordPress 5.1 or above
 * _Statify_ plugin installed and activated (1.5 or above)
 
 ## Frequently Asked Questions ##
@@ -92,9 +92,13 @@ Same for IPv6 prefixes like _2001:db8:a0b:12f0::/64_.
 
 ## Screenshots ##
 1. Statify Filter settings page
+2. Statify Filter settings page (continued)
 
 ## Upgrade Notice ##
 
+### 1.8.0 ###
+This release maintenance update that raises the minimum requirements to WordPress 5.1 and PHP 7.4.
+
 ### 1.7.2 ###
 This is a bugfix release to restore the manual cleanup function that was broken since 1.7.0.
 
@@ -107,6 +111,12 @@ This is a service release with primarily internal rework. Tested up to 6.4 and P
 
 ## Changelog
 
+### 1.8.0 / 24.05.2026 ###
+* Minimum required WordPress version is 5.1
+* Minimum required PHP version is 7.4
+* Declared compatibility with WordPress 7.0
+* Various internal code improvements
+
 ### 1.7.2 / 06.06.2024 ###
 * Restore manual database cleanup functionality
 
diff --git a/assets/screenshot-1.png b/assets/screenshot-1.png
index b03eb2c..e13ea05 100644
Binary files a/assets/screenshot-1.png and b/assets/screenshot-1.png differ
diff --git a/assets/screenshot-2.png b/assets/screenshot-2.png
new file mode 100644
index 0000000..0a41f71
Binary files /dev/null and b/assets/screenshot-2.png differ
diff --git a/composer.json b/composer.json
index 065a00c..4432586 100644
--- a/composer.json
+++ b/composer.json
@@ -1,6 +1,6 @@
 {
   "name": "stklcode/statify-blacklist",
-  "version": "1.7.2",
+  "version": "1.8.0",
   "description": "A filter extension for the famous Statify WordPress plugin",
   "keywords": [
     "wordpress",
@@ -18,17 +18,19 @@
   ],
   "type": "wordpress-plugin",
   "require": {
-    "php": ">=5.5",
-    "composer/installers": "~v1.12|~v2.3"
+    "php": ">=7.4",
+    "composer/installers": "~v2.3"
   },
   "require-dev": {
-    "dealerdirect/phpcodesniffer-composer-installer": "^v1.0",
-    "phpunit/phpunit": "^5|^6|^7|^8|^9",
-    "phpunit/php-code-coverage": "*",
+    "dealerdirect/phpcodesniffer-composer-installer": "^v1.2",
+    "phpunit/phpunit": "^8|^9",
     "slowprog/composer-copy-file": "~0.3",
-    "squizlabs/php_codesniffer": "^3.12",
+    "squizlabs/php_codesniffer": "^3.13",
+    "szepeviktor/phpstan-wordpress": "^v2.0",
+    "phpstan/extension-installer": "^1.4",
+    "phpstan/phpstan": "^2.1",
     "phpcompatibility/phpcompatibility-wp": "^2.1",
-    "wp-coding-standards/wpcs": "^3.1"
+    "wp-coding-standards/wpcs": "^3.3"
   },
   "scripts": {
     "test-all": [
@@ -43,12 +45,16 @@
     ],
     "fix-cs": [
       "phpcbf --standard=phpcs.xml"
+    ],
+    "phpstan": [
+      "phpstan analyse --memory-limit=1G"
     ]
   },
   "config": {
     "allow-plugins": {
       "composer/installers": true,
-      "dealerdirect/phpcodesniffer-composer-installer": true
+      "dealerdirect/phpcodesniffer-composer-installer": true,
+      "phpstan/extension-installer": true
     }
   }
 }
diff --git a/inc/class-statifyblacklist-admin.php b/inc/class-statifyblacklist-admin.php
index 023321b..7ceb4f6 100644
--- a/inc/class-statifyblacklist-admin.php
+++ b/inc/class-statifyblacklist-admin.php
@@ -26,7 +26,7 @@ class StatifyBlacklist_Admin extends StatifyBlacklist {
 	 *
 	 * @since 1.5.0
 	 */
-	public static function init() {
+	public static function init(): void {
 		// Add actions.
 		add_action( 'wpmu_new_blog', array( 'StatifyBlacklist_System', 'install_site' ) );
 		add_action( 'delete_blog', array( 'StatifyBlacklist_System', 'uninstall_site' ) );
@@ -36,10 +36,7 @@ public static function init() {
 			add_action( 'network_admin_menu', array( 'StatifyBlacklist_Admin', 'add_menu_page' ) );
 			add_filter(
 				'network_admin_plugin_action_links',
-				array(
-					'StatifyBlacklist_Admin',
-					'plugin_actions_links',
-				),
+				array( 'StatifyBlacklist_Admin', 'plugin_actions_links' ),
 				10,
 				2
 			);
@@ -55,7 +52,7 @@ public static function init() {
 	 *
 	 * @since 1.0.0
 	 */
-	public static function add_menu_page() {
+	public static function add_menu_page(): void {
 		$title = __( 'Statify Filter', 'statify-blacklist' );
 		if ( self::$multisite ) {
 			add_options_page(
@@ -79,14 +76,14 @@ public static function add_menu_page() {
 	/**
 	 * Add plugin meta links
 	 *
-	 * @param array  $links Registered links.
-	 * @param string $file  The filename.
+	 * @param string[] $links Registered links.
+	 * @param string   $file  The filename.
 	 *
-	 * @return array  Merged links.
+	 * @return string[] Merged links.
 	 *
 	 * @since 1.0.0
 	 */
-	public static function plugin_meta_link( $links, $file ) {
+	public static function plugin_meta_link( array $links, string $file ): array {
 		if ( STATIFYBLACKLIST_BASE === $file ) {
 			$links[] = '<a href="https://github.com/stklcode/statify-blacklist">GitHub</a>';
 		}
@@ -97,14 +94,14 @@ public static function plugin_meta_link( $links, $file ) {
 	/**
 	 * Add plugin action links.
 	 *
-	 * @param array  $links Registered links.
-	 * @param string $file  The filename.
+	 * @param string[] $links Registered links.
+	 * @param string   $file  The filename.
 	 *
-	 * @return array  Merged links.
+	 * @return string[] Merged links.
 	 *
 	 * @since 1.0.0
 	 */
-	public static function plugin_actions_links( $links, $file ) {
+	public static function plugin_actions_links( array $links, string $file ): array {
 		$base = self::$multisite ? network_admin_url( 'settings.php' ) : admin_url( 'options-general.php' );
 
 		if ( STATIFYBLACKLIST_BASE === $file && current_user_can( 'manage_options' ) ) {
@@ -124,13 +121,13 @@ public static function plugin_actions_links( $links, $file ) {
 	 *
 	 * @global wpdb $wpdb WordPress database.
 	 */
-	public static function cleanup_database() {
+	public static function cleanup_database(): void {
 		// Check user permissions.
-		if ( ! current_user_can( 'manage_options' ) && ! ( defined( 'DOING_CRON' ) && DOING_CRON ) ) {
+		if ( ! current_user_can( 'manage_options' ) && ! wp_doing_cron() ) {
 			die( esc_html__( 'Are you sure you want to do this?', 'statify-blacklist' ) );
 		}
 
-		if ( defined( 'DOING_CRON' ) && DOING_CRON ) {
+		if ( wp_doing_cron() ) {
 			$clean_ref = ( 1 === self::$options['referer']['cron'] );
 			$clean_trg = ( 1 === self::$options['target']['cron'] );
 		} else {
@@ -200,13 +197,13 @@ public static function cleanup_database() {
 	/**
 	 * Sanitize URLs and remove empty results.
 	 *
-	 * @param array $urls given array of URLs.
+	 * @param string[] $urls given array of URLs.
 	 *
-	 * @return array  sanitized array.
+	 * @return string[] sanitized array.
 	 *
 	 * @since 1.1.1
 	 */
-	private static function sanitize_urls( $urls ) {
+	private static function sanitize_urls( array $urls ): array {
 		return array_flip(
 			array_filter(
 				array_map(
diff --git a/inc/class-statifyblacklist-settings.php b/inc/class-statifyblacklist-settings.php
index 3944816..a33fc66 100644
--- a/inc/class-statifyblacklist-settings.php
+++ b/inc/class-statifyblacklist-settings.php
@@ -20,7 +20,7 @@ class StatifyBlacklist_Settings extends StatifyBlacklist {
 	 *
 	 * @return void
 	 */
-	public static function register_settings() {
+	public static function register_settings(): void {
 		register_setting(
 			'statify-blacklist',
 			'statify-blacklist',
@@ -34,7 +34,7 @@ public static function register_settings() {
 		add_settings_section(
 			'statifyblacklist-referer',
 			__( 'Referer filter', 'statify-blacklist' ),
-			null,
+			array( __CLASS__, 'section_referer' ),
 			'statify-blacklist'
 		);
 		add_settings_field(
@@ -72,7 +72,7 @@ public static function register_settings() {
 		add_settings_section(
 			'statifyblacklist-target',
 			__( 'Target filter', 'statify-blacklist' ),
-			null,
+			array( __CLASS__, 'section_target' ),
 			'statify-blacklist'
 		);
 		add_settings_field(
@@ -110,7 +110,7 @@ public static function register_settings() {
 		add_settings_section(
 			'statifyblacklist-ip',
 			__( 'IP filter', 'statify-blacklist' ),
-			null,
+			array( __CLASS__, 'section_ip' ),
 			'statify-blacklist'
 		);
 		add_settings_field(
@@ -133,7 +133,7 @@ public static function register_settings() {
 		add_settings_section(
 			'statifyblacklist-ua',
 			__( 'User agent filter', 'statify-blacklist' ),
-			null,
+			array( __CLASS__, 'section_ua' ),
 			'statify-blacklist'
 		);
 		add_settings_field(
@@ -166,7 +166,7 @@ public static function register_settings() {
 	 *
 	 * @return void
 	 */
-	public static function create_settings_page() {
+	public static function create_settings_page(): void {
 		?>
 		<div class="wrap">
 			<h1><?php esc_html_e( 'Statify Filter', 'statify-blacklist' ); ?></h1>
@@ -220,12 +220,23 @@ public static function create_settings_page() {
 	 * phpcs:disable Squiz.PHP.EmbeddedPhp.ContentAfterEnd
 	 */
 
+	/**
+	 * Options section for referer filters.
+	 *
+	 * @return void
+	 */
+	public static function section_referer(): void {
+		print '<p>';
+		esc_html_e( 'These filter rules are applied to the origin URL of the request.', 'statify-blacklist' );
+		print '</p>';
+	}
+
 	/**
 	 * Option for activating the live referer filter.
 	 *
 	 * @return void
 	 */
-	public static function option_referer_active() {
+	public static function option_referer_active(): void {
 		?>
 		<fieldset>
 			<legend class="screen-reader-text"><?php esc_html_e( 'Activate live filter', 'statify-blacklist' ); ?></legend>
@@ -245,7 +256,7 @@ public static function option_referer_active() {
 	 *
 	 * @return void
 	 */
-	public static function option_referer_cron() {
+	public static function option_referer_cron(): void {
 		?>
 		<fieldset>
 			<legend class="screen-reader-text"><?php esc_html_e( 'CronJob execution', 'statify-blacklist' ); ?></legend>
@@ -265,7 +276,7 @@ public static function option_referer_cron() {
 	 *
 	 * @return void
 	 */
-	public static function option_referer_regexp() {
+	public static function option_referer_regexp(): void {
 		?>
 		<select id="statifyblacklist-referer-regexp" name="statify-blacklist[referer][regexp]">
 			<option value="<?php print esc_attr( StatifyBlacklist::MODE_NORMAL ); ?>" <?php selected( StatifyBlacklist::$options['referer']['regexp'], StatifyBlacklist::MODE_NORMAL ); ?>>
@@ -296,7 +307,7 @@ public static function option_referer_regexp() {
 	 *
 	 * @return void
 	 */
-	public static function option_referer_blacklist() {
+	public static function option_referer_blacklist(): void {
 		?>
 		<textarea id="statifyblacklist-referer-blacklist" name="statify-blacklist[referer][blacklist]" cols="40" rows="5"><?php
 		print esc_html( implode( "\r\n", array_keys( StatifyBlacklist::$options['referer']['blacklist'] ) ) );
@@ -312,7 +323,7 @@ public static function option_referer_blacklist() {
 	 *
 	 * @return void
 	 */
-	public static function option_target_active() {
+	public static function option_target_active(): void {
 		?>
 		<fieldset>
 			<legend class="screen-reader-text"><?php esc_html_e( 'Activate live filter', 'statify-blacklist' ); ?></legend>
@@ -327,12 +338,23 @@ public static function option_target_active() {
 		<?php
 	}
 
+	/**
+	 * Options section for target filters.
+	 *
+	 * @return void
+	 */
+	public static function section_target(): void {
+		print '<p>';
+		esc_html_e( 'These filter rules are applied to the visited page.', 'statify-blacklist' );
+		print '</p>';
+	}
+
 	/**
 	 * Option for activating cron the target filter.
 	 *
 	 * @return void
 	 */
-	public static function option_target_cron() {
+	public static function option_target_cron(): void {
 		?>
 		<fieldset>
 			<legend class="screen-reader-text"><?php esc_html_e( 'CronJob execution', 'statify-blacklist' ); ?></legend>
@@ -352,7 +374,7 @@ public static function option_target_cron() {
 	 *
 	 * @return void
 	 */
-	public static function option_target_regexp() {
+	public static function option_target_regexp(): void {
 		?>
 		<select id="statifyblacklist-target-regexp" name="statify-blacklist[target][regexp]">
 			<option value="<?php print esc_attr( StatifyBlacklist::MODE_NORMAL ); ?>" <?php selected( StatifyBlacklist::$options['target']['regexp'], StatifyBlacklist::MODE_NORMAL ); ?>>
@@ -378,7 +400,7 @@ public static function option_target_regexp() {
 	 *
 	 * @return void
 	 */
-	public static function option_target_blacklist() {
+	public static function option_target_blacklist(): void {
 		?>
 		<textarea id="statifyblacklist-target-blacklist" name="statify-blacklist[target][blacklist]" cols="40" rows="5"><?php
 		print esc_html( implode( "\r\n", array_keys( StatifyBlacklist::$options['target']['blacklist'] ) ) );
@@ -389,12 +411,25 @@ public static function option_target_blacklist() {
 		<?php
 	}
 
+	/**
+	 * Options section for IP filters.
+	 *
+	 * @return void
+	 */
+	public static function section_ip(): void {
+		print '<p>';
+		esc_html_e( 'These filter rules are applied to the IP address of the visitor.', 'statify-blacklist' );
+		print '</p><p>';
+		esc_html_e( 'Cron execution is not possible for IP filter, because IP addresses are not stored.', 'statify-blacklist' );
+		print '</p>';
+	}
+
 	/**
 	 * Option for activating the live IP filter.
 	 *
 	 * @return void
 	 */
-	public static function option_ip_active() {
+	public static function option_ip_active(): void {
 		?>
 		<fieldset>
 			<legend class="screen-reader-text"><?php esc_html_e( 'Activate live filter', 'statify-blacklist' ); ?></legend>
@@ -404,8 +439,6 @@ public static function option_ip_active() {
 			</label>
 			<p class="description">
 				<?php esc_html_e( 'Filter at time of tracking, before anything is stored', 'statify-blacklist' ); ?>
-				<br>
-				<?php esc_html_e( 'Cron execution is not possible for IP filter, because IP addresses are not stored.', 'statify-blacklist' ); ?>
 			</p>
 		</fieldset>
 		<?php
@@ -416,7 +449,7 @@ public static function option_ip_active() {
 	 *
 	 * @return void
 	 */
-	public static function option_ip_blacklist() {
+	public static function option_ip_blacklist(): void {
 		?>
 		<textarea id="statifyblacklist-ip-blacklist" name="statify-blacklist[ip][blacklist]" cols="40" rows="5"><?php
 		print esc_html( implode( "\r\n", StatifyBlacklist::$options['ip']['blacklist'] ) );
@@ -428,12 +461,25 @@ public static function option_ip_blacklist() {
 		<?php
 	}
 
+	/**
+	 * Options section for user agent filters.
+	 *
+	 * @return void
+	 */
+	public static function section_ua(): void {
+		print '<p>';
+		esc_html_e( 'These filter rules are applied to the user agent (browser) identifier of the request.', 'statify-blacklist' );
+		print '</p><p>';
+		esc_html_e( 'Cron execution is not possible for user agent filter, because the user agent is stored.', 'statify-blacklist' );
+		print '</p>';
+	}
+
 	/**
 	 * Option for activating the live user agent filter.
 	 *
 	 * @return void
 	 */
-	public static function option_ua_active() {
+	public static function option_ua_active(): void {
 		?>
 		<label for="statifyblacklist-ua-active">
 			<input id="statifyblacklist-ua-active" name="statify-blacklist[ua][active]" type="checkbox" value="1" <?php checked( StatifyBlacklist::$options['ua']['active'], 1 ); ?>>
@@ -442,8 +488,6 @@ public static function option_ua_active() {
 
 		<p class="description">
 			<?php esc_html_e( 'Filter at time of tracking, before anything is stored', 'statify-blacklist' ); ?>
-			<br>
-			<?php esc_html_e( 'Cron execution is not possible for user agent filter, because the user agent is stored.', 'statify-blacklist' ); ?>
 		</p>
 		<?php
 	}
@@ -453,7 +497,7 @@ public static function option_ua_active() {
 	 *
 	 * @return void
 	 */
-	public static function option_ua_regexp() {
+	public static function option_ua_regexp(): void {
 		?>
 		<select id="statifyblacklist-ua-regexp" name="statify-blacklist[ua][regexp]">
 			<option value="<?php print esc_attr( StatifyBlacklist::MODE_NORMAL ); ?>" <?php selected( StatifyBlacklist::$options['ua']['regexp'], StatifyBlacklist::MODE_NORMAL ); ?>>
@@ -484,7 +528,7 @@ public static function option_ua_regexp() {
 	 *
 	 * @return void
 	 */
-	public static function option_ua_blacklist() {
+	public static function option_ua_blacklist(): void {
 		?>
 		<textarea name="statify-blacklist[ua][blacklist]" id="statifyblacklist-ua-blacklist" cols="40" rows="5"><?php
 		print esc_html( implode( "\r\n", StatifyBlacklist::$options['ua']['blacklist'] ) );
@@ -503,7 +547,7 @@ public static function option_ua_blacklist() {
 	 *
 	 * @return array Validated and sanitized options.
 	 */
-	public static function sanitize_options( $options ) {
+	public static function sanitize_options( array $options ): array {
 		// Extract filter lists from multi-line inputs.
 		$referer = self::parse_multiline_option( $options['referer']['blacklist'] );
 		$target  = self::parse_multiline_option( $options['target']['blacklist'] );
@@ -553,7 +597,7 @@ public static function sanitize_options( $options ) {
 	 *
 	 * @since 1.7.0
 	 */
-	private static function sanitize_referer_options( &$options ) {
+	private static function sanitize_referer_options( array &$options ): void {
 		$referer_given   = $options['blacklist'];
 		$referer_invalid = array();
 		if ( StatifyBlacklist::MODE_NORMAL === $options['regexp'] ) {
@@ -596,7 +640,7 @@ private static function sanitize_referer_options( &$options ) {
 	 *
 	 * @since 1.7.0
 	 */
-	private static function sanitize_target_options( &$options ) {
+	private static function sanitize_target_options( array &$options ): void {
 		$target_given     = $options['blacklist'];
 		$target_sanitized = $target_given;
 		if ( StatifyBlacklist::MODE_REGEX === $options['regexp'] || StatifyBlacklist::MODE_REGEX_CI === $options['regexp'] ) {
@@ -626,7 +670,7 @@ private static function sanitize_target_options( &$options ) {
 	 *
 	 * @since 1.7.0
 	 */
-	private static function sanitize_ip_options( &$options ) {
+	private static function sanitize_ip_options( array &$options ): void {
 		$given_ip             = $options['blacklist'];
 		$sanitized_ip         = self::sanitize_ips( $given_ip );
 		$ip_diff              = array_diff( $given_ip, $sanitized_ip );
@@ -647,14 +691,14 @@ private static function sanitize_ip_options( &$options ) {
 	/**
 	 * Sanitize URLs and remove empty results.
 	 *
-	 * @param array $urls given array of URLs.
+	 * @param string[] $urls given array of URLs.
 	 *
-	 * @return array  sanitized array.
+	 * @return string[] sanitized array.
 	 *
 	 * @since 1.1.1
 	 * @since 1.7.0 moved from StatifyBlacklist_Admin to StatifyBlacklist_Settings.
 	 */
-	private static function sanitize_urls( $urls ) {
+	private static function sanitize_urls( array $urls ): array {
 		return array_flip(
 			array_filter(
 				array_map(
@@ -670,14 +714,14 @@ function ( $r ) {
 	/**
 	 * Sanitize IP addresses with optional CIDR notation and remove empty results.
 	 *
-	 * @param array $ips given array of URLs.
+	 * @param string[] $ips given array of URLs.
 	 *
-	 * @return array  sanitized array.
+	 * @return string[] sanitized array.
 	 *
 	 * @since 1.4.0
 	 * @since 1.7.0 moved from StatifyBlacklist_Admin to StatifyBlacklist_Settings.
 	 */
-	private static function sanitize_ips( $ips ) {
+	private static function sanitize_ips( array $ips ): array {
 		return array_values(
 			array_unique(
 				array_filter(
@@ -706,21 +750,21 @@ function ( $ip ) {
 	/**
 	 * Validate regular expressions, i.e. remove duplicates and empty values and validate others.
 	 *
-	 * @param array $expressions Given pre-sanitized array of regular expressions.
+	 * @param string[] $expressions Given pre-sanitized array of regular expressions.
 	 *
-	 * @return array Array of invalid expressions.
+	 * @return string[] Array of invalid expressions.
 	 *
 	 * @since 1.5.0 #13
 	 * @since 1.7.0 moved from StatifyBlacklist_Admin to StatifyBlacklist_Settings.
 	 */
-	private static function sanitize_regex( $expressions ) {
+	private static function sanitize_regex( array $expressions ): array {
 		return array_filter(
 			array_flip( $expressions ),
 			function ( $re ) {
 				// Check of preg_match() fails (warnings suppressed).
 
 				// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
-				return false === @preg_match( StatifyBlacklist::regex( $re, false ), null );
+				return false === @preg_match( StatifyBlacklist::regex( $re, false ), '' );
 			}
 		);
 	}
@@ -732,7 +776,7 @@ function ( $re ) {
 	 *
 	 * @return array Parsed options.
 	 */
-	private static function parse_multiline_option( $raw ) {
+	private static function parse_multiline_option( string $raw ): array {
 		if ( empty( trim( $raw ) ) ) {
 			return array();
 		} else {
diff --git a/inc/class-statifyblacklist-system.php b/inc/class-statifyblacklist-system.php
index 2cd5473..db550c0 100644
--- a/inc/class-statifyblacklist-system.php
+++ b/inc/class-statifyblacklist-system.php
@@ -30,22 +30,13 @@ class StatifyBlacklist_System extends StatifyBlacklist {
 	 *
 	 * @return void
 	 */
-	public static function install( $network_wide = false ) {
+	public static function install( bool $network_wide = false ): void {
 		// Create tables for each site in a network.
 		if ( $network_wide && is_multisite() ) {
-			if ( function_exists( 'get_sites' ) ) {
-				$sites = get_sites();
-			} else {
-				return;
-			}
+			$sites = get_sites( array( 'fields' => 'ids' ) );
 
 			foreach ( $sites as $site ) {
-				if ( is_array( $site ) ) {
-					$site_id = $site['blog_id'];
-				} else {
-					$site_id = $site->blog_id;
-				}
-				self::install_site( $site_id );
+				self::install_site( $site );
 			}
 
 			restore_current_blog();
@@ -66,8 +57,8 @@ public static function install( $network_wide = false ) {
 	 *
 	 * @return void
 	 */
-	public static function install_site( $site_id ) {
-		switch_to_blog( (int) $site_id );
+	public static function install_site( int $site_id ): void {
+		switch_to_blog( $site_id );
 		add_option(
 			'statify-blacklist',
 			self::default_options()
@@ -83,23 +74,14 @@ public static function install_site( $site_id ) {
 	 *
 	 * @return void
 	 */
-	public static function uninstall() {
+	public static function uninstall(): void {
 		if ( is_multisite() ) {
 			$old = get_current_blog_id();
 
-			if ( function_exists( 'get_sites' ) ) {
-				$sites = get_sites();
-			} else {
-				return;
-			}
+			$sites = get_sites( array( 'fields' => 'ids' ) );
 
 			foreach ( $sites as $site ) {
-				if ( is_array( $site ) ) {
-					$site_id = $site['blog_id'];
-				} else {
-					$site_id = $site->blog_id;
-				}
-				self::uninstall_site( $site_id );
+				self::uninstall_site( $site );
 			}
 
 			switch_to_blog( $old );
@@ -117,9 +99,9 @@ public static function uninstall() {
 	 *
 	 * @return void
 	 */
-	public static function uninstall_site( $site_id ) {
+	public static function uninstall_site( int $site_id ): void {
 		$old = get_current_blog_id();
-		switch_to_blog( (int) $site_id );
+		switch_to_blog( $site_id );
 		delete_option( 'statify-blacklist' );
 		switch_to_blog( $old );
 	}
@@ -131,7 +113,7 @@ public static function uninstall_site( $site_id ) {
 	 *
 	 * @return void
 	 */
-	public static function upgrade() {
+	public static function upgrade(): void {
 		self::update_options();
 		// Check if config array is not associative (pre 1.2.0).
 		if ( array_keys( self::$options['referer'] ) === range( 0, count( self::$options['referer'] ) - 1 ) ) {
diff --git a/inc/class-statifyblacklist.php b/inc/class-statifyblacklist.php
index 375ce7d..3685bd1 100644
--- a/inc/class-statifyblacklist.php
+++ b/inc/class-statifyblacklist.php
@@ -78,7 +78,7 @@ class StatifyBlacklist {
 	 *
 	 * @return void
 	 */
-	public static function init() {
+	public static function init(): void {
 		// Skip on autosave.
 		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
 			return;
@@ -99,7 +99,7 @@ public static function init() {
 		}
 
 		// Statify uses WP AJAX as of 1.7, so we need to reach this point. But there are no further admin/cron actions.
-		if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
+		if ( wp_doing_ajax() ) {
 			return;
 		}
 
@@ -109,7 +109,7 @@ public static function init() {
 		}
 
 		// CronJob to clean up database.
-		if ( defined( 'DOING_CRON' ) && DOING_CRON &&
+		if ( wp_doing_cron() &&
 			( 1 === self::$options['referer']['cron'] || 1 === self::$options['target']['cron'] ) ) {
 			add_action( 'statify_cleanup', array( 'StatifyBlacklist_Admin', 'cleanup_database' ) );
 		}
@@ -121,11 +121,11 @@ public static function init() {
 	 * @since 1.0.0
 	 * @since 1.2.1 update_options($options = null) Parameter with default value introduced.
 	 *
-	 * @param array $options Optional. New options to save.
+	 * @param array|null $options Optional. New options to save.
 	 *
 	 * @return void
 	 */
-	public static function update_options( $options = null ) {
+	public static function update_options( ?array $options = null ): void {
 		if ( self::$multisite ) {
 			$o = get_site_option( 'statify-blacklist' );
 		} else {
@@ -141,7 +141,7 @@ public static function update_options( $options = null ) {
 	 *
 	 * @return array The options array.
 	 */
-	protected static function default_options() {
+	protected static function default_options(): array {
 		return array(
 			'referer' => array(
 				'active'    => 0,
@@ -173,9 +173,9 @@ protected static function default_options() {
 	 *
 	 * @since 1.0.0
 	 *
-	 * @return bool TRUE if referer matches filter.
+	 * @return bool|null TRUE if referer matches filter.
 	 */
-	public static function apply_blacklist_filter() {
+	public static function apply_blacklist_filter(): ?bool {
 		// Referer filter.
 		if (
 		self::apply_single_filter(
@@ -225,7 +225,7 @@ public static function apply_blacklist_filter() {
 	 *
 	 * @since 1.6 Extracted from "apply_blacklist_filter" to reduce redundancies.
 	 */
-	private static function apply_single_filter( $config, $value_fn ) {
+	private static function apply_single_filter( array $config, callable $value_fn ): bool {
 		// Is the filter active?
 		if ( ! isset( $config['active'] ) || 0 === $config['active'] ) {
 			return false;
@@ -276,12 +276,12 @@ private static function apply_single_filter( $config, $value_fn ) {
 	/**
 	 * Preprocess regular expression provided by the user, i.e. add delimiters and optional ci flag.
 	 *
-	 * @param string|array $expression       Original expression string or array of expressions.
-	 * @param string|array $case_insensitive Make expression match case-insensitive.
+	 * @param string|string[] $expression       Original expression string or array of expressions.
+	 * @param bool            $case_insensitive Make expression match case-insensitive.
 	 *
 	 * @return string Preprocessed expression ready for preg_match().
 	 */
-	protected static function regex( $expression, $case_insensitive ) {
+	protected static function regex( $expression, bool $case_insensitive ): string {
 		$res = '/';
 		if ( is_string( $expression ) ) {
 			$res .= str_replace( '/', '\/', $expression );
@@ -309,7 +309,7 @@ function ( $e ) {
 	 *
 	 * @return string The referer.
 	 */
-	private static function get_referer() {
+	private static function get_referer(): string {
 		$referer = wp_get_raw_referer();
 		if ( ! $referer ) {
 			$referer = '';
@@ -323,10 +323,10 @@ private static function get_referer() {
 	 *
 	 * @return string Referer domain.
 	 */
-	private static function get_referer_domain() {
+	private static function get_referer_domain(): string {
 		$referer = wp_parse_url( self::get_referer() );
 
-		return strtolower( ( isset( $referer['host'] ) ? $referer['host'] : '' ) );
+		return strtolower( $referer['host'] ?? '' );
 	}
 
 	/**
@@ -334,7 +334,7 @@ private static function get_referer_domain() {
 	 *
 	 * @return string The referer.
 	 */
-	private static function get_target() {
+	private static function get_target(): string {
 		if ( isset( $_SERVER['REQUEST_URI'] ) ) {
 			$target = filter_var( wp_unslash( $_SERVER['REQUEST_URI'] ), FILTER_SANITIZE_URL );
 			if ( $target ) {
@@ -386,7 +386,7 @@ private static function get_ip() {
 	 *
 	 * @return string The user agent string.
 	 */
-	private static function get_user_agent() {
+	private static function get_user_agent(): string {
 		if ( ! empty( $_SERVER['HTTP_USER_AGENT'] ) ) {
 			$user_agent = filter_var( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) );
 			if ( $user_agent ) {
@@ -405,7 +405,7 @@ private static function get_user_agent() {
 	 *
 	 * @return bool TRUE, if the given IP addresses matches the given subnet.
 	 */
-	private static function cidr_match( $ip, $net ) {
+	private static function cidr_match( string $ip, string $net ): bool {
 		if ( substr_count( $net, ':' ) > 1 ) {  // Check for IPv6.
 			if ( ! ( ( extension_loaded( 'sockets' ) && defined( 'AF_INET6' ) ) || inet_pton( '::1' ) ) ) {
 				return false;
diff --git a/package.json b/package.json
index 025b0e1..03551a6 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "statify-blacklist",
-  "version": "1.7.2",
+  "version": "1.8.0",
   "description": "A filter extension for the famous Statify WordPress plugin",
   "author": "Stefan Kalscheuer",
   "license": "GPL-2.0+"
diff --git a/phpcs.xml b/phpcs.xml
index 1e0c607..a146c36 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -10,7 +10,7 @@
 	<file>inc</file>
 
 	<!-- Compliance with WordPress Coding Standard -->
-	<config name="minimum_supported_wp_version" value="4.7"/>
+	<config name="minimum_supported_wp_version" value="5.1"/>
 	<rule ref="WordPress">
 		<!-- Direct queries used to clean up statify table. -->
 		<exclude name="WordPress.DB.DirectDatabaseQuery.DirectQuery"/>
@@ -19,11 +19,13 @@
 
 	<rule ref="WordPress.WP.I18n">
 		<properties>
-			<property name="text_domain" type="array" value="statify-blacklist"/>
+			<property name="text_domain" type="array">
+				<element value="statify-blacklist"/>
+			</property>
 		</properties>
 	</rule>
 
 	<!-- PHP compatibility level -->
-	<config name="testVersion" value="5.5-"/>
+	<config name="testVersion" value="7.4-"/>
 	<rule ref="PHPCompatibilityWP"/>
 </ruleset>
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..db99a07
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,10 @@
+parameters:
+  level: 5
+  paths:
+    - inc/
+    - statify-blacklist.php
+  ignoreErrors:
+    - message: '/^Constant STATIFYBLACKLIST_BASE not found\.$/'
+      path: inc/
+    - message: '/^Parameter \#1 \$text of function esc_attr expects string, int given\.$/'
+      path: inc/class-statifyblacklist-settings.php
diff --git a/statify-blacklist.php b/statify-blacklist.php
index 1cb2219..a666174 100644
--- a/statify-blacklist.php
+++ b/statify-blacklist.php
@@ -3,21 +3,22 @@
  * Statify Filter
  *
  * @package     PluginPackage
- * @author      Stefan Kalscheuer <stefan@stklcode.de>
+ * @author      Stefan Kalscheuer
  * @license     GPL-2.0+
  *
  * @wordpress-plugin
  * Plugin Name:       Statify Filter
  * Plugin URI:        https://wordpress.org/plugins/statify-blacklist/
  * Description:       Extension for the Statify plugin to add customizable filters. (formerly "Statify Blacklist")
- * Version:           1.7.2
- * Requires at least: 4.7
- * Requires PHP:      5.5
- * Requires Plugins:  statify
+ * Version:           1.8.0
+ * Requires at least: 5.1
+ * Requires PHP:      7.4
  * Author:            Stefan Kalscheuer (@stklcode)
  * Author URI:        https://www.stklcode.de
- * Text Domain:       statify-blacklist
  * License:           GPLv2 or later
+ * License URI:       https://www.gnu.org/licenses/gpl-2.0.html
+ * Text Domain:       statify-blacklist
+ * Requires Plugins:  statify
  *
  * Statify Filter is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -69,7 +70,7 @@
  *
  * @since 1.0.0
  */
-function statify_blacklist_autoload( $class_name ) {
+function statify_blacklist_autoload( string $class_name ): void {
 	$plugin_classes = array(
 		'StatifyBlacklist',
 		'StatifyBlacklist_Admin',
@@ -93,9 +94,9 @@ function statify_blacklist_autoload( $class_name ) {
  *
  * @return boolean Whether minimum WP and PHP versions are met.
  */
-function statify_blacklist_compatibility_check() {
-	return version_compare( $GLOBALS['wp_version'], '4.7', '>=' ) &&
-		version_compare( phpversion(), '5.5', '>=' );
+function statify_blacklist_compatibility_check(): bool {
+	return version_compare( $GLOBALS['wp_version'], '5.1', '>=' ) &&
+		version_compare( phpversion(), '7.2', '>=' );
 }
 
 /**
@@ -105,7 +106,7 @@ function statify_blacklist_compatibility_check() {
  *
  * @return void
  */
-function statify_blacklist_disable() {
+function statify_blacklist_disable(): void {
 	if ( is_plugin_active( STATIFYBLACKLIST_BASE ) ) {
 		deactivate_plugins( STATIFYBLACKLIST_BASE );
 		add_action( 'admin_notices', 'statify_blacklist_disabled_notice' );
@@ -124,13 +125,13 @@ function statify_blacklist_disable() {
  *
  * @return void
  */
-function statify_blacklist_disabled_notice() {
+function statify_blacklist_disabled_notice(): void {
 	echo '<div class="notice notice-error is-dismissible"><p><strong>';
 	printf(
 		/* translators: minimum version numbers for WordPress and PHP inserted at placeholders */
 		esc_html__( 'Statify Filter requires at least WordPress %1$s and PHP %2$s.', 'statify-blacklist' ),
-		'4.7',
-		'5.5'
+		'5.1',
+		'7.2'
 	);
 	echo '<br>';
 	printf(
diff --git a/test/StatifyBlacklist_Settings_Test.php b/test/StatifyBlacklist_Settings_Test.php
index 10b5d6d..1bd5dd3 100644
--- a/test/StatifyBlacklist_Settings_Test.php
+++ b/test/StatifyBlacklist_Settings_Test.php
@@ -19,7 +19,7 @@ class StatifyBlacklist_Settings_Test extends PHPUnit\Framework\TestCase {
 	 *
 	 * @return void
 	 */
-	public function test_sanitize_options() {
+	public function test_sanitize_options(): void {
 		global $settings_error;
 
 		// Emulate default submission: nothing checked, all textareas empty.
@@ -215,7 +215,7 @@ public function test_sanitize_options() {
 	 *
 	 * @return void
 	 */
-	public function test_sanitize_ips() {
+	public function test_sanitize_ips(): void {
 		// IPv4 tests.
 		$valid   = array( '192.0.2.123', '192.0.2.123/32', '192.0.2.0/24', '192.0.2.128/25' );
 		$invalid = array( '12.34.56.789', '192.0.2.123/33', '192.0.2.123/-1' );
@@ -276,7 +276,7 @@ public function test_sanitize_ips() {
 	 *
 	 * @return void
 	 */
-	public function test_register_settings() {
+	public function test_register_settings(): void {
 		global $settings;
 		$settings = array();
 
diff --git a/test/StatifyBlacklist_System_Test.php b/test/StatifyBlacklist_System_Test.php
index b9de750..cc51ece 100644
--- a/test/StatifyBlacklist_System_Test.php
+++ b/test/StatifyBlacklist_System_Test.php
@@ -19,7 +19,7 @@ class StatifyBlacklist_System_Test extends PHPUnit\Framework\TestCase {
 	 *
 	 * @return void
 	 */
-	public function test_upgrade() {
+	public function test_upgrade(): void {
 		// Create configuration of version 1.3.
 		$options13 = array(
 			'active_referer' => 1,
diff --git a/test/StatifyBlacklist_Test.php b/test/StatifyBlacklist_Test.php
index f454a04..725e22d 100644
--- a/test/StatifyBlacklist_Test.php
+++ b/test/StatifyBlacklist_Test.php
@@ -22,7 +22,7 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 	 *
 	 * @return void
 	 */
-	public function test_referer_filter() {
+	public function test_referer_filter(): void {
 		// Prepare Options: 2 filtered domains, disabled.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -89,7 +89,7 @@ public function test_referer_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_referer_regex_filter() {
+	public function test_referer_regex_filter(): void {
 		// Prepare Options: 2 regular expressions.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -151,7 +151,7 @@ public function test_referer_regex_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_referer_keyword_filter() {
+	public function test_referer_keyword_filter(): void {
 		// Prepare Options: 2 regular expressions.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -209,7 +209,7 @@ public function test_referer_keyword_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_cidr_match() {
+	public function test_cidr_match(): void {
 		// IPv4 tests.
 		$this->assertTrue( invoke_static( StatifyBlacklist::class, 'cidr_match', array( '127.0.0.1', '127.0.0.1' ) ) );
 		$this->assertTrue( invoke_static( StatifyBlacklist::class, 'cidr_match', array( '127.0.0.1', '127.0.0.1/32' ) ) );
@@ -311,7 +311,7 @@ public function test_cidr_match() {
 	 *
 	 * @return void
 	 */
-	public function test_ip_filter() {
+	public function test_ip_filter(): void {
 		// Prepare Options: 2 filtered IPs, disabled.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -388,7 +388,7 @@ public function test_ip_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_target_filter() {
+	public function test_target_filter(): void {
 		// Prepare Options: 2 filtered domains, disabled.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -466,7 +466,7 @@ public function test_target_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_ua_filter() {
+	public function test_ua_filter(): void {
 		// Prepare Options: 2 filtered IPs, disabled.
 		StatifyBlacklist::$options = array(
 			'referer' => array(
@@ -531,7 +531,7 @@ public function test_ua_filter() {
 	 *
 	 * @return void
 	 */
-	public function test_combined_filters() {
+	public function test_combined_filters(): void {
 		// Prepare Options: simple referer + simple target + ip.
 		StatifyBlacklist::$options = array(
 			'referer' => array(