On PHPRiot.com today there's a new tutorial teaching you about singleton classes in PHP and how they can be used to simplify things in your application.

In this PhpRiot Snippet I will show you how to create and use singleton classes. A singleton class is a class that can instantiated once only. While it may not come up frequently, it can be a useful technique when it simply doesn't make sense to have than one instance of a class.

He shows how, by following a few rules, you can make a sample class that will only create and pass back a new instance of itself if ones doesn't already exist. It's a simple concept, but it can come in quite handy in the right situations. Just be sure you use them wisely.