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Date: Wed, 7 Sep 2016 20:27:10 +0200
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Subject: Re: [PHP-DEV] RFC - Immutable classes
From: cmbecker69@gmx.de ("Christoph M. Becker")

On 07.09.2016 at 20:11, Fleshgrinder wrote:

> On 9/7/2016 8:57 AM, Michał Brzuchalski wrote:
>
>> AFAIK CoW in case of objects would be impossible to implement.
> 
> Nothing is impossible. :)
> 
> We have full access to the real object inside of zend_std_write_property
> and can easily clone it, perform the desired changes and return without
> affecting anyone.
> 
> I am not 100% sure how to do this without fiddling around a bit.
> 
> @nikic and @afaults: I am really sorry to bother you both but you guys
> simply know the PHP source endlessly good. What do you think, would it
> be possible to implement copy-on-write for an object as we have it with
> our scalar and compound types?
> 
>     final class A {
>       public $p;
>     }
> 
>     $a = new A;
>     $b = $a;
> 
>     var_dump($a === $b); // bool(true)
> 
>     $b->p = 1;
> 
>     var_dump($a === $b); // bool(false)
> 
> It's only about writing to existing properties.

Ah, good old PHP 4, see <https://3v4l.org/VaD1W#v5328>. :-)

-- 
Christoph M. Becker