In no particular order these external resources supplement the tutorial by providing shortcuts to commonly used information and further learning.
A Session In The Cookie Jar
Sessions and cookies – how to keep track of visitors to your site.
An introduction to PHP’s easiest method for dealing with XML.
Bugging Out – Part 1
Basic error handling.
The Trashman Cometh – Part 1
A primer in basic security.
The Trashman Cometh – Part 2
Putting the pieces together – a first Web application.
No News is Good News
Creating a simple RSS news aggregator.