public function _clean()
    {
        $be = Kwf_Cache_Simple::getBackend();
        if ($be == 'memcache') {
            return Kwf_Cache_Simple::getMemcache()->flush();
        } else if ($be == 'file') {
            foreach (glob('cache/view/*') as $i) {
                unlink($i);
            }
            return true;
        } else {
            return self::getZendCache()->clean();
        }
    }