Get client using ip address, works fine in intranet and DNS and reverse proxyes

getClientHostname.php

$proxy = (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : false;
        $hostname = "";
        if (!!$proxy) {
            $ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
            $hostname .= "Proxy: ";
        } else {
            $ipaddress = $_SERVER['REMOTE_ADDR']; //
        }
        if ($ipaddress == $hostname) {
            $hostname .= "Unknown";
        } else {
            $hostname .=  gethostbyaddr($ipaddress);;
        }
        return $hostname;