public function isCached($id) {
        if ($id != null) {
            $id = $this->getIDfromOjb($id);
        }

        if ($id == null)
            return false;

        $cachefile = $this->getConfig('cacheDir') . '/' . utf8_decode($id);
        $cachetime = $this->getConfig('cacheTime');

        if (file_exists($cachefile) && time() - $cachetime < fileatime($cachefile)) {
            return true;
        }

        return false;
    }