public function getIpAddress()
    {
        foreach ($this->headers as $k)
        {
            if (isset($this->server[$k]))
            {
                // header can be comma separated
                $ips = explode(',', $this->server[$k]);
                $ip = trim(end($ips));
                $ip = filter_var($ip, FILTER_VALIDATE_IP);
                if (false !== $ip)
                {
                    return $ip;
                }
            }
        }

        // no valid ip found
        return false;
    }