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

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.