--TEST-- Testing several valid and invalid parameters --FILE-- <?php class foo { } var_dump(class_exists('')); var_dump(class_exists(NULL)); var_dump(class_exists('FOO')); var_dump(class_exists('bar')); var_dump(class_exists(1)); var_dump(class_exists(new stdClass)); ?> --EXPECTF-- bool(false) bool(false) bool(true) bool(false) bool(false) Warning: class_exists() expects parameter 1 to be string, object given in %s on line %d NULL