Description:
------------
Seems like ArrayObject with ARRAY_AS_PROPS implementation broken.

After second call of constructor I cant get access to the array property.

Test script:
---------------
for ($i = 0; $i<2; $i++) {
	$data = new \ArrayObject(new stdClass(), ArrayObject::ARRAY_AS_PROPS);

	$data->itemType = 'bulletin';

	var_dump(!is_null($data['itemType']));
}
exit;

Expected result:
----------------
bool(true) bool(true) 

Actual result:
--------------
bool(true) bool(false)