Ok, how many of you have noticed this (probably a lot.)
The correct spelling is "Referrer." But PHP doesn't see it that way. The reason is probably because of this:
http://dictionary.reference.com/search?q=referer
Now I don't blame them for using the commonly misspuleded word but they should at least be consistant. Look at this page in the manual. http://www.php.net/manual/en/ref.session.php
They use it both ways! Do a search on the site, there's referrer and referer all over the place. Is it unreasonable to ask them to fix this? Or at least be consistant. I admit my spelling isn't greate but this is killing me. I found the problem in dreamweaver with it's auto code popdowns. I started typing $HTTP_ and it gave me a popdown with "REFERER" in it, when I clicked on it, it actually put "REFERRER" on the page, which doesn't exist. phpinfo prefers "referer"