PHP & Proxy Servers
The PHP _SERVER variable contains the IP of the remote client.$ip = $_SERVER['REMOTE_ADDR']
REMOTE_ADDR
You may be tempted to decide your clients IP by using REMOTE_ADDR but this will be the IP of any reverse proxy server if one is being used[REMOTE_ADDR] => 10.10.10.30
HTTP_X_FORWARDED_FOR
Instead use HTTP_X_FORWARDED_FOR which is a list of IPs and (normal) proxy servers your client used to reach your site[HTTP_X_FORWARDED_FOR] => 10.10.10.10, 10.10.10.20
