Introduction

As the clever PHP developer that you surely are, it's quite probable that you've already used the object-oriented paradigm to develop one or more web applications. This implies that defining a few classes along with their methods and properties should be a pretty familiar procedure to you. Definitely, it must be admitted that building object-based applications with a friendly scripting language like PHP is not only a truly educational experience, since it requires at least a basic knowledge of software engineering, but fun as well. 

As you possibly know, after a decent time working with this approachable -- yet mature -- web development language, it's possible to create scripts that implement a certain level of complexity, particularly when it comes to defining different relationships between several objects. And now that I mentioned the term "relationship," I'm pretty sure that you'll be familiar with the two main pillars of this huge area of object-oriented programming. I mean aggregation and composition.

However, while learning to aggregate and compose classes with PHP (or any other programming language, naturally) can be a significant step toward mastering the fundamentals of software development, it's fair to say that these two proven models of object interaction would be rather pointless if inheritance is deliberately left out of the learning process.

Perhaps, at the moment of reading the previous sentence you feel inclined to congratulate yourself, since you have already worked with parent and child classes here and there during the creation of a given PHP application. But one question is in order here: can inheritance be used in some way that is simpler than the traditional one, even with the purpose of doing something as trivial as building dynamic, object-oriented web pages?

To your satisfaction (and mine, of course) the answer to the above question is a resounding yes! Actually, by using the basic principles of inheritance, it's feasible to create entire, consistent-looking web sites, with only a little effort and an intermediate background in object-oriented programming.

So, now that I have introduced this instructive subject, in the two articles in this series I'm going to show you how to build a sample object-based web site from its bare bones structure, by using the encapsulated logic of some parent and child PHP 5 classes. In this way I'll demonstrate how inheritance can be used to tackle a concrete project, such as constructing dynamic web pages.

All right, it's time to move forward and start learning how to utilize a simple classes hierarchy to create an expandable web site. Let's begin now!