public static function getInstance()
    {
        // set strict to false
        // -> meaning: no matter which parameter given we return the same instance
        self::$strict = false;

        // get possible parameter passed to this class
        $arguments = func_get_args();

        // decide call-type by given parameter
        if (empty($arguments)) {
            $instance = parent::getInstance();
        } else {
            $instance = parent::getInstance($arguments);
        }

        // return instance
        return $instance;
    }