Here’s a tutorial worth looking at if you’re as unfamiliar as we are — that’s “pretty darn unfamiliar indeed”, that is — with server programming:
In this article, work through the entire process of building an iPhone chat application from the server all the way to the user interface on the front end…
The iPhone side is all completely bog standard SDK you’re probably familiar with, so it’s a nice example of how a very little bit of PHP server code can be used to handle some realish-time communication needs with PHP and just a dash of SQL and XML. Nifty!
And if this is indeed something that would be handy for you, check out the author’s other articles while you’re there. Lots of XMLy and PHPy and so on webby goodness there, looks like.