If you've been writing mostly procedural PHP code and are looking to make that "next step" up to working with objects and classes (OOP), you should check out this detailed tutorial introducing you to some of the primary OOP-in-PHP concepts.

Object oriented programming (OOP) was first introduced in php4. Area for oop in php version 4 was not very vast. There were only few features available in php4. Major concept of the object oriented programming in PHP is introduced from version 5(we commonly known as php5). [...] But still in php5 object model is designed nicely. If you have good understanding of OOP then you can create very good architecture of your php application. You only need to know some of the basic principles of object oriented programming and how to implement that concept of oop in php.

While the wording is slightly odd in some spots (English doesn't seem to be the author's first language), it's' a great introduction to the major OOP-related topics including:

• Classes and Objects
• Visibility in PHP
• Abstract classes and interfaces
• Object cloning
• Method chaining

Each section also has downloadable code to go along with the examples, making it easier to follow and test out the actual scripts.