I just discovered something regarding $HTTP_GET_VARS. Hope this helps.
Ok. This the scenario. I have an anchor tag on a page with a query string "threadID=2":
<a href="page2.php?threadID=2">...</a> say.
Also on the same page, I have a variable $threadID. For some reason, when I do
<? print "$HTTP_GET_VARS[threadID]"; ?> on page2.php, it returns nothing.
So I changed the query string name to something else, eg:
<a href="page2.php?n_threadID=2">...</a>
And <? print "$HTTP_GET_VARS[n_threadID]"; ?>
works perfectly!!!
Moral of the story: "Play safe! Make all variables unique where possible!"