Object custom serializing infrastructure

I have added the callbacks to class_entry structure and patches to serialization mechanism to allow custom object serialization/unserialization inside the PHP serialize mechanism. Purpose: -------- Define possibility for custom serialization and userialization of PHP5 objects, which would allow users to run custom code when objects are serialized and unserialized. Implementation: --------------- Define 2 callbacks for zend_class_entry, as follows: int (*serialize)(zval *object, unsigned char **buffer, zend_uint *buf_len, zend_serialize_data *data TSRMLS_DC); Serializes object data into the buffer. Should serialize only object "internals", not class name. zend_serialize_data is the variables hash that var.c uses to track references. If you want to use it, consult var.c and use it the same way. int (*unserialize)(zval **object, const unsigned char *buf, zend_uint buf_len, zend_unserialize_data *data TSRMLS_DC); creates new zval according to the serialized data in buf, buf_len limits data length. Returns SUCCESS if object created correctly, FAILURE if it failed. Data include only the object data, not class name, etc. zend_unserialize_data is the variables hash that var_unserialize.re uses to track references. If you want to use it, consult var.c and use it the same way. By default, these callbacks are NULL, meaning the standard mechanism is used. Format ------ New serialization is using letter 'C' to designate custom serialization data. Example ------- Attached in the example patch for SimpleXML that demonstrates the concept by using callbacks to serialize SimpleXML object's data as XML and then restoring it to the object back. This should allow, for example, to seamlessly put SimpleXML object to a session data.