I see a problem with this idea.
In case we support constant expressions, we should support constants in such
expressions, but the values of these constants may be unknown in compile
time.
<?php
class Foo {
const A = 0;
}
?>
<?php
require_once "foo.php";
class Bar extends Foo {
const B = self::A + 1;
}
?>
Delaying constant initialization for expressions in general will require
keeping of Abstaract Syntax Tree, that should be evaluated at run-time by
zval_update_constant().
Thanks. Dmitry.
> -----Original Message-----
> From: Nuno Lopes [mailto:[EMAIL PROTECTED]
> Sent: Saturday, September 08, 2007 10:50 PM
> To: Stanislav Malyshev
> Cc: internals@lists.php.net; [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: Re: Re: [PHP-DEV] constant folding optimization
>
>
> >> I made a patch to implement constant folding optimization in the
> >> Zend engine.
> >> The patch is available at:
> >> http://web.ist.utl.pt/nuno.lopes/zend_constant_folding.txt
> >
> > I like the idea a lot, however I think this patch has one
> > significant downside - as far as I understand, it doesn't enable
> > constant expressions in constant contexts. I.e. I can do $a = 2+2
> > and get it evaluated but I can't do function foo($a = 2+2)
> or const
> > $a = 2+2. If we moved this to the parser level I think we could do
> > both.
>
> Well we don't support that syntax at this moment. If you are saying
> that we could add support for such syntax.. it does seem a
> good idea,
> but in that case we would need to modify a few rules of the grammar
> (like adding a const_expr production, and allow static_scalar derive
> it, etc..).
>
> If others agree with this syntax, I can take a look in
> implementing it.
>
> Nuno
>
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