Description:
------------
See the code for best description, what happens...

Reproduce code:
---------------
class Bar extends ArrayObject {
    private $foo = array( 1, 2, 3 );
    function __construct() 
    {
       parent::__construct($this->foo);
    }
}

$foo = new Bar();
var_dump($foo);
object(Bar)#1 (3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}

$foo['foo'] = 23;
var_dump($foo);
object(Bar)#1 (4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  ["foo"]=>
  int(23)
}

$bar = new Bar();
var_dump($bar);
object(Bar)#2 (4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  ["foo"]=>
  int(23)
}

Expected result:
----------------
The second instance should have a clean array instead of the array which the first one got.