Accessing Global Variables in a helper

[eluser]Freewolf[/eluser]
Hey I tried using $_SERVER['HTTP_REFERER'] in a helper and got an error saying that http_referer was not a valid index. Is there a special way that $_SERVER variables need to be accessed in a helper?

[eluser]KarlBallard[/eluser]
Why not just user the user_agent library?

[eluser]Unknown[/eluser]
So.... how would one access global variables in a helper?