class_exists Checks if the class has been defined boolclass_exists stringclass_name boolautoload The autoload parameter was added in PHP 5 This function returns &true; if the class given by class_name has been defined, &false; otherwise. class_exists will attempt to call __autoload by default, if you don't want class_exists to call __autoload(), you can set the parameter autoload to &false;. ]]> See also get_declared_classes.