Javascript lets you do it if you use the equality (==) instead of the identity (===).. i think.
Unfortunately it's replaced by something even more messed up
Edit: It's true in PHP though. :-/
Can you post exactly what you did in PHP that shows "NULL" is equal to NULL? There's quite a few approaches like ==, ===, and is_null(). I can't get any to think "NULL" is NULL, though I imagine I'm missing something.