Description:
------------
Attempting to compare two variables containing a reference to an object instance which in turn contains a property static or otherwise, referring back to itself produces a "Nesting level too deep" fatal error. One example where a self references may be necessary is a singleton: in PHP 5.1.6 the reproduce code works as expected. A feature, or a bug?

Reproduce code:
---------------
    $obj = Singleton::instance();
    $obj2 = $obj;

    var_dump($obj != $obj2);

    class Singleton
    {
        private static $instance;
        
        private function __construct()
        {
            $this->me = $this;
        }

        public static function instance()
        {
            if (! self::$instance) {
                self::$instance = new Singleton;
            }

            return self::$instance;
        }
    }

Expected result:
----------------
bool(false)

Actual result:
--------------
Fatal error: Nesting level too deep - recursive dependency? in crash-test.php on line 5