How to activate http referer from server / cpanel?

My issue is about $_SERVER['HTTP_REFERER']. I can't get the value of http_referer on开发者_Go百科 my server or may be due to Firefox. But I've also printed print_r($_SERVER); but still it doesn't provide me previous page's link.

This is directly from PHP.net

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.

I'm thinking it may be a firefox issue. What version are you using?