public static function guid_bin($existed = null)
    {
        if (is_string($existed)) {
            $guid = trim($existed, '{}');
            if (preg_match(static::GUID_REGEX, $guid)) {
                return hex2bin(str_replace([' ', '-'], '', $guid));
            }
        }
        mt_srand((double)microtime() * 1000);
        $uniqid = uniqid(rand(), true);
        return md5($uniqid, true);
    }