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Date: Tue, 17 Aug 2010 10:46:04 +0200
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To: RQuadling@googlemail.com
Cc: Jingcheng Zhang <diogin@gmail.com>, php-dev <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Static initialization block support in Class?
From: info@tyrael.hu (Ferenc Kovacs)

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 Tue, Aug 17, 2010 at 10:04 AM, Richard Quadling <rquadling@gmail.com>wrote:

> On 17 August 2010 08:39, Jingcheng Zhang <diogin@gmail.com> wrote:
> > Hello internals,
> >
> > I wonder whether it is possible to implement "static initialization
> block"
> > feature in PHP, for example:
> >
> > <?php
> > class Foo {
> >
> > }
> > class Bar {
> >    public static $baz = 'baz';
> >    public static $foo;
> >    static {
> >        // After loading this file, self::$foo is initialized as a Foo
> > instance.
> >        self::$foo = new Foo();
> >    }
> > }
> > ?>
> >
> > Currently we have to do this outside the class definition as static
> variable
> > initialization is only limited to constant values.
> > However in some circumstance, "dynamic" initialization of static variable
> is
> > expected and meaningful.
> >
> > Thanks in advance!
> >
> > --
> > Best regards,
> > Jingcheng Zhang
> > P.R.China
> >
>
> Implementing a singleton method is a common solution and one that is
> well understood and documented.
>
> Another option would be to put the initialisation immediately after
> the class definition, so once the class is loaded, a static instance
> is prepared. This saves the consumer of the class from having to do 1
> additional line of code.
>
> Or you could load the public static methods with a JIT call to prepare
> the static instance. Overhead is that every call will have to test
> self::$instance
>
>
> There is probably some argument against "statics" being "dynamic"
> though ... not my area of expertise to argue either way.
>
> --
> Richard Quadling.
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>
This was brought up in the past:
http://www.mail-archive.com/internals@lists.php.net/msg46458.html
I still think that it's weird, that I can define a constant to a dynamic
value (eg. by a complex expression or a function's return value), but I
can't do that with the class consts. and with 5.3, we have two different
kind of consts, you can define constants in compile time with const where
you can't use expressions, and you can use the define method, where you can
use expressions.
and you can combine them:

define("NOW", time());
var_dump(NOW);
const BAR = NOW;
var_dump(BAR);
class baz{
  const BAR = NOW;
}
var_dump(baz::BAR);'

with that in mind, I think we could allow complex expression to the const:
the expression will be stored as-is, and when it's referenced (JIT) then it
will be evaluated.

and this could be used also for variables also:

class foo{
  public $now = time();
}
$foo = new foo;
echo $foo->now;

ps: I predict somebody will say: can of worms! :)

Tyrael

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