Description:
------------
Given that $object['foo'] is an empty string, empty($object['foo']) returns FALSE, if $object is an instance of a class that extends ArrayObject. It returns TRUE on an instance of ArrayObject or an implementation of ArrayAccess.

It never calls offsetGet() on the extended ArrayObject.

Test script:
---------------
<?php

class ArrayObjectChild extends ArrayObject {
 
  public function offsetExists($offset) {
    var_dump('Called: '.__METHOD__);
    return parent::offsetExists($offset);
  }

  public function offsetGet($offset) {
    var_dump('Called: '.__METHOD__);
    return parent::offsetGet($offset);
  }
}

$object = new ArrayObjectChild(array('foo' => ''));
var_dump(empty($object['foo']));

Expected result:
----------------
string(38) "Called: ArrayObjectChild::offsetExists" 
string(35) "Called: ArrayObjectChild::offsetGet" 
bool(true)

Actual result:
--------------
string(38) "Called: ArrayObjectChild::offsetExists" 
bool(false)