private function isLocalIp ()
    {
        $ip = $this->serverData["REMOTE_ADDR"];

        if (!is_string($ip))
        {
            return false;
        }

        if (in_array($ip, ['127.0.0.1', 'fe80::1', '::1'], true))
        {
            return true;
        }

        // allowed (= local) IPs include
        // 10.0.0.0 – 10.255.255.255
        // 172.16.0.0 – 172.31.255.255
        // 192.168.0.0 – 192.168.255.255
        return 1 === preg_match("/^(10\\.|192\\.168\\.|172\\.(1[6-9]|2[0-9]|3[0-1])\\.)/", $ip);
    }