Environment Variables -- HTTP_REFERER

Hello, I am running PHP 4.0.6 in a Windows XP environment. I need to know a better and more reliable way to check which page the user came from before the page he/she has currently accessed. I tried to look at HTTP_REFERER, but PHP says it is unreliable. Is there a better way? Here is what PHP has to say about HTTP_REFERER: 'HTTP_REFERER' The address of the page (if any) which referred the user agent to the current page. This is set by the user agent. Not all user agents will set this, and some provide the ability to modify HTTP_REFERER as a feature. In short, it cannot really be trusted. Any help would be greatly appreciated. Darwin