PHP Lambda based memoizer

memoize.php

<?php

// Lambda based memoizer
function memoize($fn) {
  $cache = array();
  return function ($key) use($fn, &$cache) {
    if (!isset($cache[$key])) {
      $cache[$key] = $fn($key);
    }
    return $cache[$key];
  };
}

// Simple usage
$m = memoize(function ($key) {
  return "[$key]";
});

var_dump($m('one'));
var_dump($m('two'));
var_dump($m('one'));

// Usage with class
class Test {
  public function __construct() {
    $this->m = memoize(function ($key) {
      return "[$key]";
    });
  }
  public $m;
}
$t = new Test;

// http://stackoverflow.com/questions/7067536/how-to-call-a-closure-that-is-a-class-variable
var_dump($t->m->__invoke('one'));
var_dump($t->m->__invoke('two'));
var_dump($t->m->__invoke('one'));