On the Zend Developer Zone, there's a new post pointing to the second part of their look at the Manning Publishing book "PHP in Action".

If you've been anxiously awaiting part two of this series then your wait is over. Here's a short introduction to the section part of this series written by the author of the book, Dagfinn Reiersol. I had the privilege of meeting Dagfinn at phpuk last week. Below the introduction is the link I know you’ve been waiting for.

The new PDF they link to focus on two different patterns - the Decorator (a wrapper class) pattern and the Null Object (an object that works like the others but does nothing behind the scenes) pattern.