Something

function getIP() {

if (getenv("HTTP_CLIENT_IP")) $ip = getenv("HTTP_CLIENT_IP");
else if(getenv("HTTP_X_FORWARDED_FOR")) $ip = getenv("HTTP_X_FORWARDED_FOR");
else if(getenv("REMOTE_ADDR")) $ip = getenv("REMOTE_ADDR");
else $ip = "UNKNOWN";

return $ip;
}