Classes that implement this interface no longer support __sleep() and __wakeup(). The method serialized is called whenever an instance needs to be serialized. This does not invoke __destruct() or has any other side effect unless programmed inside the method. When the data is unserialized the class is known and the appropriate unserialize() method is called as a constructor instead of calling __construct(). If you need to execute the standard constructor you may do so in the method.
