In addition to REMOTE_ADDR
and HTTP_X_FORWARDED_FOR
there are some other headers that can be set such as:
HTTP_CLIENT_IP
HTTP_X_FORWARDED_FOR
can be comma delimited list of IPsHTTP_X_FORWARDED
HTTP_X_CLUSTER_CLIENT_IP
HTTP_FORWARDED_FOR
HTTP_FORWARDED
I found the code on the following site useful:
http://www.grantburton.com/?p=97