Anthony Ferrara has a new post to his site about a concept from functional programming - monads - and how he's tried to bring them to PHP with a bit of proof of concept code.

Lately I've been playing around with some functional languages and concepts. I have found that some of these concepts are directly applicable in the OOP code that I've been writing. One of those concepts that I think is worth talking about is the Monad. This is something that every functional developer tries to write a tutorial on, because it's such a cool but hard to grasp concept. This post is not really going to be a Monad tutorial per se, but more of a post about bringing the general concept to OOP, and what that looks like.

He starts off with a brief definition of what a "monad" is, defining it as a sort of "state container." He then gets into the examples (using this code) showing how to create a Monad and bind functionality to it. He walks through some examples of the transformations you can do with it and introduces the ListMonad as an alternative for looping.