Getting website referrer

I'm trying to echo a phrase to visitors to my site who are coming from one of my other sites. So something simple like IF $_SERVER['HTTP_REFERER'] = website.com { echo "hello website.com visitor"; }

If anyone can help me out here would be greatly appreciated.

 

if (strpos($_SERVER['HTTP_REFERER'], 'website.com')) {
echo 'yo';
}

PHP:

 

many thanks deception..works like a charm

 

isn't there a way for the user to "turn off" that variable though?

 

Yeah there is and if they do I don't know of any way to know where they came from really, that's mostly the best you can do