New BC surface to explore: serialization of objects

[Ocramius]

Example:

class MySerializablePayload {
-    private string $foo;
+    private int $foo;
}

or:

class MySerializablePayload {
    private ValueType $foo;
}

class ValueType {
-    private string $foo;
+    private int $foo;
}

This is extremely interesting to research, but also a very complex and useful to inspect BC surface.