A while ago, I covered The Observer Pattern, a really useful pattern, particularly when it comes to event-handling systems.
Today, I’m going to take a look at the Composite Pattern, another really useful pattern that allows you to treat individual objects and collections of those objects as if they were the same. That may sound a little strange, but we’ll look at a concrete example, which should help clarify things: a List-based system.
The Observer Pattern is probably one of my favourite patterns.
It’s fairly straightforward, flexible, and best of all, the base classes you need to implement the Observer Pattern are available in the Standard PHP Library, so it should be available to all PHP5 applications.
Let’s jump straight in, and take a look at a possible scenario where we could use this pattern.