Using "X-Forwarded-For" in Apache or PHP

Using "X-Forwarded-For" in Apache or PHP:

Modifying Apache's Log Format

Well, Joe has a post describing how to obtain this value in IIS. But that doesn't really help if you're not running IIS and like me have chosen to run a little web server you may have heard of called Apache.

Configuring Apache to use the X-Forwarded-For instead of (or in conjunction with) the normal HTTP client header is pretty simple.ApacheWeek has a great article on how to incorporate custom fields into a log file, but here's the down and dirty. Open your configuration file (usually in /etc/httpd/conf/) and find the section describing the log formats. Then add the following to the log format you want to modify, or create a new one that includes this to extract the X-Forwarded-For value:

    %{X-Forwarded-For}i

That's it. If you don't care about the proxy IP address, you can simply replace the traditional %h in the common log format with the new value, or you can add it as an additional header. Restart Apache and you're ready to go.