http://www.blackhatworld.com/blackhat-seo/php-perl/527166-share-very-simple-script-testing-your-current-proxy-anonymity.html
$_SERVER['HTTP_X_FORWARDED_FOR'] , $_SERVER['HTTP_VIA'], $_SERVER['X-REAL-IP'], $_SERVER['HTTP_X_PROXY_ID'] , $_SERVER['HTTP_CLIENT_IP']
if (!empty($_SERVER['HTTP_CLIENT_IP']))
{
$ip=$_SERVER['HTTP_CLIENT_IP'];
}
elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
{
$ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
}
else
{
$ip=$_SERVER['REMOTE_ADDR'];
}
<?php
if (!empty($_SERVER["HTTP_CLIENT_IP"]))
{
//check for ip from share internet
$ip = $_SERVER["HTTP_CLIENT_IP"];
}
elseif (!empty($_SERVER["HTTP_X_FORWARDED_FOR"]))
{
// Check for the Proxy User
$ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
}
else
{
$ip = $_SERVER["REMOTE_ADDR"];
}
// This will print user's real IP Address
// does't matter if user using proxy or not.
echo "IPv4: ".$ip;
$via = $_SERVER['HTTP_VIA'];
$realip= $_SERVER['X-REAL-IP'];
$proxyid = $_SERVER['HTTP_X_PROXY_ID'];
echo "<br/>Via: ".$via;
echo "<br/>realip: ".$realip;
echo "<br/>proxyid: ".$proxyid;
$hostname = gethostbyaddr($_SERVER['REMOTE_ADDR']);
echo "<br/>Hostname: ".$hostname;
?>