PHP Anthology, Volume 1, Chapter 2. Object Oriented PHP

In this chapter, you’ll gain a practical grounding in writing object oriented PHP—and there’ll be plenty of opportunities to get your hands dirty. There are many ways to teach OOP, and the topic provides endless room for discussion. In my opinion, the best approach is to dive in head first, seeing how procedural tasks can be accomplished with classes in PHP, and adding the theory as we go. This is the approach we’ll take in this chapter. Throughout both volumes of The PHP Anthology, I’ll be using OOP, where appropriate, which should give you further examples to study. In particular, Chapter 7, Design Patterns should provide some insight into why OOP is an effective way to structure your applications.

In practice, learning to use the object model provided by PHP requires us to achieve two goals, which usually have to be undertaken simultaneously:

The first step is easy. It’s the subject of the next solution, and further examples appear in later solutions that look at more advanced subjects.

The second step, the “mental leap”, is both easy and challenging. Once you achieve it, you will no longer think about long lists of tasks that a single script should accomplish; instead, you’ll see programming as the putting together of a set of tools to which your script will delegate work.

In the above script, we’ve called directly PHP’s MySQL functions, which act on the variables we pass to them. This generally results in our getting back a new variable with which we can perform further work.

An object oriented approach to solving the same problem might look like this:

<?php
// OOP Example
// Include MySQL class
require_once 'Database/MySQL.php';
// Instantiate MySQL class, connect to MySQL and select database
$db = new MySQL('localhost', 'harryf', 'secret', 'sitepoint');
// Perform a query selecting five articles
$sql = 'SELECT * FROM articles LIMIT 0,5';
$result = $db->query($sql); // Creates a MySQLResult object
// Display the results
while ($row = $result->fetch()) {
  // Display results here
}
?>

The object oriented approach really shows its worth in situations in which objects interact with each other. I’ll leave further discussion of that to the solutions in this chapter, but it’s an important concept. As you become fluent in object oriented programming, you’ll find that writing complex applications becomes as easy as putting together blocks of Lego.