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Date: Wed, 04 Feb 2004 12:09:50 +0200
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Subject: New destructors implementation
From: andi@zend.com (Andi Gutmans)

We've changed the way that objects are destroyed during shutdown to a 
2-phase mechanism.  First, destructors are called for all of the objects in 
the store (in no particular order).  Afterwards - the object storage and 
the various symbol tables are destroyed&freed.

This has several implications:

1.  The dependency problems during shutdown which could cause destructors 
not to be called under certain circumstances - are gone now.  Destructors 
are always called for all objects, and you can depend on that.

2.  A *VERY* important implication is that you cannot, and must not rely in 
any way on the order of destruction during shutdown.  It runs in no 
particular order.  That means that by the time the destructor for your 
object $foo is called,  a reference to some other object $bar may already 
be post-destruction.  Note that it will still be 'intact' and accessible in 
the sense that if you access it - there won't be crashes.  However, if this 
object does indeed have a destructor, it can be considered semantically 
wrong to touch this object at this point.

3.  The APIs have changed to allow for this new mechanism.  Instead of the 
previous dtor callback, which was supposed to both call the destructor and 
free the object's storage, there are now two separate callbacks - dtor 
(call the destructor) and free_storage (guess).  Generally, for classes 
which implement PHP-style objects, you should implement both of these 
callbacks (though you can probably use the standard dtor callback).  For 
overloaded classes such as SimpleXML, COM, etc. - you will most likely only 
have to implement the free_storage callback, as there's no destructor 
per-se.  We already went over all the overloaded classes in the php-src CVS 
and moved most of the dtor callbacks to free_storage.  Note that the 
interface is slightly different between these two callbacks - free_storage 
doesn't receive the object handle.

4.  Last but not least - bug #25541 is now fixed! :)

Andi