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Hello Internals,
Has anyone given thought to a feature that allows (PHP) developer to
invalidate classes (allowing the developer to re-load the class, with
modified code)? I realize that this is not possible now, and for good
reason. But I think the idea has potential.
I asked Sara about this, yesterday, after the idea occurred to me, and
she graciously whipped up a small extension that does exactly what I'm
looking for, but she told me she thought it was a bad idea to be doing
this (and also allows destruction of functions). I agree: without the
proper safety nets, this is a dangerous thing to be doing.
So, why do I want this functionality, in the first place? Consider a
long-running application (not a web page, but, for instance, a
sockets-based application). It would be very useful for me, as a
developer, to be able to re-load parts of the application, without
tossing the whole current instance of PHP (and all associated resources)
- -- ie, doesn't release socket connections, but allows re-loading of the
associated handlers. This could be accomplished by invalidating a class
(destroying it, and marking all instanciated objects with a special type
(__PHP_Destroyed_Class comes to mind, after __PHP_Incomplete_Class), and
re-declaring the class.
- -- sample code (working) --
<?php
eval('Class Foo { function name() { echo "Foo\n"; } }');
Foo::name();
shiva_destroy_class('Foo');
eval('Class Foo { function name() { echo "Bar\n"; } }');
Foo::name();
?>
- -- output --
Foo
Bar
I also spoke (typed) with Stig, who told me that this sounds more like a
PHP 6 feature. I understand that class destruction breaks a lot of
assumptions. As Sara pointed out, it will definitely break optimizers.
Also, the potential for segfault is very high:
Class Foo { function name() { echo "Foo\n"; } }; $Foo = new Foo();
shiva_destroy_class('Foo'); eval('Class Foo { function name() { echo
"Bar\n"; } };'); $Foo->name(); results in segfault..
I'm, admittedly, completely out of my league here.. I played with the
API a little, and was reminded of this. (-:
It may seem like a stupid idea at first, but I think there's some value
in re-loading pieces of code, and with the proper object
counting/invalidation, sounds like it could be safe, but like I said, I
don't know what I'm doing.
Is this worth further discussion?
S
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