Re: RFC - Immutable classes
| From: | Christoph M. Becker | Date: | Wed, 07 Sep 2016 18:27:10 +0000 |
| Subject: | Re: RFC - Immutable classes | ||
| References: | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | Groups: | php.internals |
| Request: | Send a blank email to internals+get-95764@lists.php.net to get a copy of this message | ||
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