Array-like object allowing any serializable keys

AnyKeyArray.php

<?php
class AnyKeyArray implements ArrayAccess, Iterator, Countable {
  private $values = array();
  
  // ArrayAccess
  
  function offsetSet($key, $value) {
    $this->values[serialize($key)] = $value;
  }
  
  function offsetGet($key) {
    return $this->values[serialize($key)];
  }
  
  function offsetExists($key) {
    return array_key_exists(serialize($key), $this->values);
  }
  
  function offsetUnset($key) {
    unset($this->values[serialize($key)]);
  }
  
  // Iterator
  
  function rewind() {
    reset($this->values);
  }
  
  function valid() {
    return (key($this->values) !== null);
  }
  
  function current() {
    return current($this->values);
  }
  
  function key() {
    return unserialize(key($this->values));
  }
  
  function next() {
    next($this->values);
  }
  
  // Countable
  
  function count() {
    return count($this->values);
  }
  
}

The strange thing is that you cannot use foreach to iterate over array with special keys. I found it when I read the changelog for PHP 5.5.