Just a minor point of criticism; require and include are statements, not functions. Not that it's a big deal or something, but I just thought I would let you know.
I'm surprised this hasn't gotten more fanfare. As age-old as this question is, I only figured out the answer just over a month ago. I've been programming in PHP for several years. It may seem like a rather idiotic thing for me to not know, but I'm glad to see this show up regardless.