Until PHP 5.3, modules weren't fully supported. But since the introduction of PHP 5.3, we can use PHP namespaces to implement the module pattern. For historical reasons, we're going to present how namespaces were used before PHP 5.3, but you should strive to use a PHP version that supports PHP namespaces. The best choice is always going to be the latest stable version of PHP.
A common approach is to use a first-level namespace that identifies your company. This will help in avoiding conflicts with third-party libraries. If you're using PSR-0, you'll have a real folder for the namespace; if you're using PSR-4, you don't need it. We'll go deeper into this shortly. But first, let's take a look at the PHP namespacing conventions.