zend_register_class() overwrites ce->create_object with parent_ce->create_object?

If I define a descendant class, I *obviously* know what create_object should do, as this should only effect internal classes. So could anybody please explain to me why the parent's create_object is enforced? It causes to write hacks like: ---8<--- zend_class_entry *ce; zend_object_value (*__create_object)(zend_class_entry *ce TSRMLS_DC); INIT_CLASS_ENTRY(ce, "classname", php_my_method_entry); ce.create_object = php_my_object_new; /* hack starts here */ __create_object = parent_ce->create_object; parent_ce->create_object = php_my_object_new; php_my_class_entry = zend_register_internal_class_ex(&ce, parent_ce, NULL TSRMLS_CC); parent->create_object = __create_object; --->8--- If this limitation is there without a really good reason, I'd like to get rid of it. Thanks, Mike