Description:
------------
Function isset does not work identically for object created by ArrayObject(). For example code I have this output :


object(ArrayObject)[1]
  public 'aa' => string 'some content' (length=12)

ko : isset does not work after ArrayObject()

object(stdClass)[2]
  public 'aa' => string 'some content' (length=12)

ok : isset work after (object)

Reproduce code:
---------------
$content = array('aa' => 'some content');

// ********************************* //

$prm = new ArrayObject($content);
var_dump($prm);

if (isset($prm->aa) === true) echo 'ok : isset work after ArrayObject()';
else echo 'ko : isset does not work after ArrayObject()';

// ********************************* //

$prm = (object) $content;
var_dump($prm);

if (isset($prm->aa) === true) echo 'ok : isset work after (object)';
else echo 'ko : isset does not work after (object)';


Expected result:
----------------
Same behavior for both use.