protected function _wfile($file, $content = '', $mode = 'wb', $lock = LOCK_EX) {
        if ($fp = fopen($file, $mode)) {
            flock($fp, $lock);
            $re = fwrite($fp, $content);
            $re2 = fclose($fp);

            if ($re !== false && $re2 !== false) {
                return true;
            }
        }

        return false;
    }