Description:
------------
Hello.

I use PHP session. When I use private or protected members in my class and don't use magic method __sleep(), PHP serialization will serialize all members and their values into PHP session correctly.
But when I use the same class and implement magic method __sleep(), PHP serialization will serialize correctly ONLY public members. Private and protected members (that I want serialize - I specified them in array returned from __sleep() function) have NULL value.
In my example's result is string from session file generated by PHP.

T.Zkoumalek

Reproduce code:
---------------
class Test
{
    private   $a = "Variable a";
    protected $b = "Variable b";
    public    $c = "Variable c";
    public    $d = "This need not be saved.";


    // Save only $a, $b, $c.
    function __sleep()
    {
        return Array( "a", "b", "c" );
    }
}

session_start();
$_SESSION[ "test" ] = new Test();

Expected result:
----------------
test|O:4:"Test":3:{s:7:" Test a";s:10:"Variable a";s:4:" * b";s:10:"Variable b";s:1:"c";s:10:"Variable c";}

Actual result:
--------------
test|O:4:"Test":3:{s:1:"a";N;s:1:"b";N;s:1:"c";s:10:"Variable c";}