function set_background_repeat($val)
    {
        if (is_null($val)) {
            $val = self::$_defaults["background_repeat"];
        }

        //see __set and __get, on all assignments clear cache, not needed on direct set through __set
        $this->_prop_cache["background_repeat"] = null;
        $this->_props["background_repeat"] = $val;
    }