Iterators in the Simplest Sense: An Accessible Implementation in PHP 4

Introduction

Design Patterns are, in my humble opinion, a very large and complex topic within the universe of software engineering, and certainly when applied particularly to PHP programming, they’re not the exception to the rule. If you’re making your first leaps into the theory and practical implementation of Design Patterns, you may find some of them easier to learn, while others might be harder to grasp, which simply means you'll need to take more time to master their concepts.

In either case, learning Design Patterns doesn’t have to be a boring and annoying experience which must be avoided at all costs. Indeed, it’s possible to introduce the topic in a friendly way, without appealing to complex definitions or including a lot of buzzwords that may eventually lead you to think erroneously that Design Patterns are out of reach of the average PHP programmer.

However, as you probably know, Design Patterns are a huge topic, which unfortunately can't be appropriately covered in a few short articles. Bearing in mind this limitation, I’ll start to teach you about Patterns by explaining some of the theory related to the Iterator pattern; at the same time (here’s where things can be interesting for you), I will emphasize its concrete implementation through some specific PHP hands-on examples, which can be quite useful for larger PHP applications.

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.

After introducing the subject of this series, it’s time to move on and begin learning how the Iterator pattern can work for you. Ready to work with Iterators? Right, let’s get started.