New handler for retrieving properties when object is serialized

Hi, I have just sent this PR: https://github.com/php/php-src/pull/397 It's reaction to the comment from nikic in PR: https://github.com/php/php-src/pull/393 The patch is about adding new object handler that is used when object is serialized. Currently this needs to be done using get_properties which is sometimes a bit over kill. It's useful in situation if you only need to change properties for serialization. It's very similar to get_debug_info that is used only in specific situations (print_r...) Currently I call it get_serialize_info . It was the first name that came to my mind. :) I am happy to change if someone has a better idea? Any thoughts? Jakub