Juan Treminio has a new post to his site introducing the ideas behind Pimple and service containers, two very similar approaches to dependency management in your applications.
Recently I've picked up the Silex framework for a project I'm building. It uses a service container for managing dependencies in your application [Pimple], which is great for defining (not instantiating) objects and their default behaviors in a single location, rather than sprinkled throughout your code in a multitude of places. [...] Using Pimple you can define several hundreds of objects, and then easily instantiate them using the container object.
He goes through some example code showing how to use Pimple to create and manage the dependencies by creating several instances of DateTime objects. He shows how this can then be "upgraded" to a service container by defining something like a PDO object (database connection) inside it. He also mentions some of the benefits that come with its use - easy resource swapping, simpler mocking for testing and allows the use of the Inversion of Control pattern.