Getting client info through proxies

[Vigilante]

How do yuo get the users ip and hostname when $HTTP_SERVER_VARS['REMOTE_ADDR'] and REMOTE_HOST are not defined?

I seem to recall something like HTTP_X_FORWARDED_BY but can't remember the exact usage. Should I just use getenv('REMOTE_ADDR') and trust php to get this for me for restrictive networks such as schools?

[Weedpacket]

Generally speaking, you can't - that's what proxy servers are for. That and the fact that a given person behind the server might not have a well-defined ip, such as those with dialup connections, having instead one that changes from connection to connection.

[Duey]

if your having problems with people spamming etc. just ban the proxy ip
using a .htaccess or just do something simple like sticking a cookie on the computer of the proxy users