Server signature is one of the easiest way to find what type of operating system and Apache version is used in a web server. But this is also dangerous when coming to security, whenever a hacker comes to know what type of server and apache version,
To getting the Real IP Address of client in PHP is very simple using following function, even if user is behind a proxy server.
else if (!empty($_SERVER[‘HTTP_X_FORWARDED_FOR’]))
//check IP is pass from proxy