--TEST-- Testing interface_exists() --FILE-- <?php interface foo { } var_dump(interface_exists('foo')); var_dump(interface_exists(1)); var_dump(interface_exists(NULL)); var_dump(interface_exists(new stdClass)); ?> --EXPECTF-- bool(true) bool(false) bool(false) Warning: interface_exists() expects parameter 1 to be string, object given in %s on line %d NULL