How can I detect if the user is on localhost in PHP?

Question

In other words, how can I tell if the person using my web application is on the server it resides on? If I remember correctly, PHPMyAdmin does something like this for security reasons.

Answer 1

$_SERVER["REMOTE_ADDR"] should tell you the user's IP. It's spoofable, though.

Check this bounty question for a very detailed discussion.

I think what you remember with PHPMyAdmin is something different: Many mySQL Servers are configured so that they can only be accessed from localhost for security reasons.

Answer 2

You can also use $_SERVER['HTTP_HOST'] for which domain name/host is the client requesting. This is much reliable because when the client needs to request, it will need to send the actual host like GET example.com in the HTTP headers.

$whitelist = array('localhost','127.0.0.1');

if(!in_array($whitelist,$_SERVER['HTTP_HOST'])){
    // not valid
}