True and False are boolean values and should only ever exist as such.
You and your silly two valued logic. Now go away or I shall taunt you a second time!
I never said True and False were the only boolean values!
Update: You didn't actually say that. But that's how you should have replied to this post, if I were to respect your opinion at all, not that you'd care whether or not I respect your opinion, nor do I care whether you care ...
Really though, thank goodness we don't have to say if ( $is_foo == TRUE ) (although, sadly, some "programmers" still do...)