Stefan Mischook has another article in the latest edition of the Web Developer Magazine (a UK publication) - the November 2006 edition - talking about how to learn OOP in PHP.
In this tutorial, you will be guided (step-by-step) through the process of building and working with objects using php's built-in OOP capabilities.
Some of the topics he covers include comparing the "old way" of making an application to the new OOP way, some of the basics about OOP, and when it's a good idea to use OOP in your applications.
It's broken down into "easily digestible steps" and there are screenshots included all over to help you along the way. If you've been looking on a resource on how to get into object-oriented programming in PHP, you'd do well to pick up a copy of this month's edition.