[RFC] Phasing out Serializable

Hi internals, Picking up a loose thread: https://wiki.php.net/rfc/custom_object_serialization introduced a replacement for Serializable in PHP 7.4, so it's time to think about deprecating and removing the old mechanism: https://wiki.php.net/rfc/phase_out_serializable This RFC follows a rather conversative approach. In PHP 8.1 there will be a deprecation warning if Serializable is implemented without also implementing __serialize() and __unserialize(). In PHP 9.0, support for Serializable is dropped internally, and only the interface retained. In PHP 10.0 the interface is dropped as well. Regards, Nikita