This April, 2000 article by Luis Argerich introduces Object Oriented Programming in PHP an explains the concepts behind data type abstraction, inheritance and polymorphism as it related to PHP.

This tutorial talks about array properties in PHP classes and how to refactor them.

This refactoring tutorial will talk about how to do refactoring on methods of PHP classes.

This article takes a look at class design with PHP4 along with some of the available classes and how to use them in your code.

This column by Rod Kreisler explains what classes are, why they are useful and how to use them in PHP. He then goes through with the creation of sample classes providing code so you can see the methodology behind it all.

This tutorial will recommend class conventions which the author considers best practices.

Some concrete examples of using object oriented principles in PHP along with plenty of sample code that helps guide you through the learning process.

This article presents programs that aid in code documentation, as well as tips on how to better document your code so that it is more useful to both yourself and others.

Learn a quick introduction to OOP (Object Oriented Programming). This tutorial will create a small class for fun to demonstrate how it all works.