Description:
------------
This is related to a bug that was fixed in version 5.2.0, which you 
can read about here:

http://bugs.php.net/bug.php?id=36759

Basically if you were to initiate a class, the destruct order would be 
incorrect: "C1,C2,C3,D1,D2,D3". This was corrected in 5.2.0 to be 
"C1,C2,C3,D3,D2,C1".

The problem, however, still persists if you create an object inside a 
static object. Code to recreate this issue is included in this bug 
report.

If you initiate the classes without the Registry singleton, it 
destructs properly ($c1 = new class1()...).

Testing this with 5.1.6, the destruct order is incorrect in both 
situations (as i'd expect). If you unset the objects in reverse order 
as they were created, both work correctly on 5.1.6 and 5.2.6.

So a work-around for either version is to simply track the objects and 
unset them. But if you don't do this, the destruct order is still 
incorrect if creating your objects through a singleton object.

Reproduce code:
---------------
class shorten {
	public function __construct() { print 'C:' . get_class($this) . "<br />"; }
	public function __destruct() { print 'D:' . get_class($this) . "<br />"; }	
}
class class1 extends shorten {}
class class2 extends shorten {}
class class3 extends shorten {}
class Registry {	
	static private $instance = null;
	private $registered = array();
    static public function instance() {
        if(self::$instance == null) self::$instance = new Registry();
        return self::$instance;
    }
	private function __call($name, $arguments) {
		if( ! isset($this->registered[$name]) ) $this->registered[$name] = new $name();
		return $this->registered[$name];
	}
	private function __get($name) {
		if( ! isset($this->registered[$name]) ) $this->registered[$name] = new $name();
		return $this->registered[$name];
	}
}
Registry::instance()->class1();
Registry::instance()->class2();
Registry::instance()->class3();

Expected result:
----------------
C:class1
C:class2
C:class3
D:class3
D:class2
D:class1

Actual result:
--------------
C:class1
C:class2
C:class3
D:class1
D:class2
D:class3