Description:
------------
I have two classes: 
- one parent with a private property
- one child that extends the parent

When i serialize the child property I get the following 
error:

Notice: serialize(): "privateProperty" returned as member 
variable from __sleep() but does not exist in test.php on 
line 30

I already know of serializable interface. But the problem 
still persist also using this interface... 
If I define a serialize method in the parent class, 
get_object_vars and reflection api do not return the 
privateProperty value... they continue to think we are 
into the scope of the child class (when we are instead 
into the parent class).





Reproduce code:
---------------
<?

class P {

        private $privateProperty;

        public function __construct() {
                $this->privateProperty = "myValue";
        }


        public function __sleep() {

                return array('privateProperty');
        }

}

class D extends P {

        public function __construct() {
                parent::__construct();
        }

}


$obj = new D();

$s = serialize($obj);
echo $s;


?>


Expected result:
----------------
I expect no warning should be raised and the echo should 
print this:

O:1:"D":1:{s:15:"privateProperty";s:7:"myValue";}



Actual result:
--------------
Notice: serialize(): "privateProperty" returned as member 
variable from __sleep() but does not exist in test.php on 
line 30
O:1:"D":1:{s:15:"privateProperty";N;}