getting proxy ip address using php

getting the details of proxy server ip address from which the users has connected to web page is as easy as getting ipaddress of the user using php

<?php
$pipaddress = getenv(HTTP_X_FORWARDED_FOR);
$ipaddress = getenv(REMOTE_ADDR);
echo "Your Proxy IPaddress is : ".$pipaddress. "(via $ipaddress)" ;
?>