I had a bit of a problem with my PHP coding tonight, and after playing 3 hours of Wii and heading back to the computer, I figured out the problem. (Newbies: This is a sound troubleshooting technique. Not necessarily playing Wii, but doing something totally different.)

I've got a question now:
If one page calls another and the other page calls the first, what will the server do to prevent a D.O.S. situation? On my machine, Apache hits 100% CPU utilization and stays there until the cooling fan turns on and I shut it down.

I don't think the server will do something about it. It will execute the code you write. Most languages 'allow' this. Only some interpreters/compilers will check for this type of bug, often by putting in a counter. If it hits some large maximum, the code will abort.

Hiawatha is the only server that stops it (its a more secure apache)