memoize.php

<?php

/**
 * Call a function but memoize the results.
 *
 * @param $callback
 *   The function to call.
 * @param $arguments
 *   The arguments to pass to callback
 */
function memoize($callback) {
  $args = array_slice(func_get_args(), 1);
  
  // Serializing is slow but allows us to accept any arguments
  $key = 'memoize-'.md5(serialize($callback).serialize($args));
  
  $item = cache_get($key);
  if ($item) {
    return $item->data;
  }
  
  $result = call_user_func_array($callback, $args);
  cache_set($key, $result);
  return $result;
}