Closure

Intent

Close over the free variables of a function. Save the state for future use.

Motivation

We want to maintain the history of computation, an maybe save and reuse the computation

Implementation

php 5.3 implements anonymous functions, albeit verbously, with explicit declaration of variables to close over

Example

$y = ...;
x = function() use ($y){
   ....
}

Note

In some sense, closures and objects are dual, compare behaviour with state and state with behaviour

Yet another note:

Alternatively have a look at this implementation or my emulating closures in php blurb