Extension Object Pattern implementation for php - uses call overloading (on which i mistakenly called bs a while back) and the reflection API:

• skeleton code here

I use a variation on this to implement Façade-like objects that present one unified interface to clients whilst delegating requests to appropriate helper objects (extensions) as they come in. You can register new extensions and all the rest. Add context awareness to the extensions (pass a reference to the parent) and you've got a clean implementation of mixins.

In reality it's an Extension Object implementation as opposed to a Façade, because façades need provide a high-level interface to a low-level subsystem, whereas this does nothing of the sort.

Façades are used all over the place, including sessions and web services. Extensions are a way of getting round the fact that PHP doesn't implement either multiple inheritance or mixins. They are also dynamic, so you can shape the capabilities of an object to fit its context.