DevShed has published the first in a new series that looks to explain the implementation and core concepts behind using iterators in PHP. This time, they look at creating this environment in PHP4.
Here, I'm not going to offer a full reference for what each design pattern is. You can buy a book to learn that, or even do some "googling" and find other helpful resources that probably will treat the subject much more extensively. Instead, I'll provide you with a concise explanation of what an Iterator is, in conjunction with numerous sample codes, which hopefully will help you understand much more easily how it can applied in PHP object-oriented programming.
They start off by looking at what the Iterator pattern is - the setup of a pseudo-class and an explaination of how it works. They follow this with a functional example and creating a subclass off of the generic base class.