apache - PHP $_SERVER['REMOTE_ADDR'] empty

Question

Somehow $_SERVER['REMOTE_ADDR'] returns an empty string, i have the same code (as part of a script) running on multiple servers and it works everywhere else, they are all the same setup.

The weird thing is, when I restart apache and load the page, it works exactly once, if I reload the site + all the times after that, it's empty. I've had other people try, same result, empty.

someone suggested it was something with IPv6 configuration, I have now completely disabled IPv6 but the problem persists.

Answer 1

if you're behind a proxy server, you can use $_SERVER['HTTP_X_FORWARDED_FOR'] or $_SERVER['HTTP_CLIENT_IP'] instead of $_SERVER['REMOTE_ADDR']. this will depends on how your proxy is configured.