Collection::map()

gistfile1.php

<?php

class Collection extends ArrayObject {

  /**
   * $callback(mixed $value, mixed $key, Iterator $iterator)
   */
  public function map(Closure $callback) {
        $iterator = $this->getIterator();
        $result = new static();
        iterator_apply($iterator, function($iterator) use($callback, $result) {
            $value = $iterator->current();
            $key = $iterator->key();
            if($status = $callback($value, $key, $iterator)) {
                $result[$key] = $value;
            }
            return $status;
        }, array($iterator));
        return $result;
    }

}