WebReference.com has this new article posted today with an exceprt from the Prentice Hall book "Core Web Application Development with PHP and MySQL".

This portion is part of chapter 13 - "Web Applications and the Internet", and focuses on a general look at computing, the web, how things are connected, the HTTP protocol, telnet debugging, mime types, SSL, and a few other protocols.

It's a decent overview, but nothing that anyone that's spent much time around PHP or the internet hasn't learned already...