Get last page visited

Question

I need to know if a person that comes to my website went from an another specific website. Example:

• User A visits www.youtube.com/myvideo and clicks on a link

Answer 1

Why not add a GET variable to the link on youtube - www.yoursite.com/?referrer=youtube

For discretion and appearance you could rewrite the URL to something like www.yoursite.com/youtube

Answer 2

The HTTP referer header is the only way. This is the data that is given to you in PHP via $_SERVER['HTTP_REFERER'].

Note that this header will work in most cases. Also note that it can be easily spoofed.