Redirecting by hostname

I'm trying to use the code below to redirect a certain hostname (in this case splitrock.net) to a different website (in this case www.test.com) As it is now, I am (using splitrock.net) not being redirected at all. This code will be prepended to every document on my server to prevent certain people from accessing it. $Redirect_Page="http://test.com"; if(ereg("splitrock.net$","$REMOTE_ADDR||$REMOTE_HOST")){header("location : $Redirect_Page");}