&reftitle.runtime; &extension.runtime; &Name; &Default; &Changeable; &Changelog; unserialize_callback_func &null; PHP_INI_ALL &ini.php.constants; &ini.descriptions.title; unserialize_callback_func string The callback specified is called when unserialize attempts to use an undefined class. A warning appears if the specified callback function is not defined, or if the callback function fails to define the missing class. See also unserialize and Autoloading Objects.