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[RFC][Discussion] Closure optimizations

php.internals

Ilija Tovilo

213 days ago

Hi everyone

A week ago, I sent an e-mail to internals regarding two closure
optimizations with some subtle BC breaks. [1] While nobody objected, I
decided to create a short RFC anyway to avoid any possible controversy
due to the BC breaks. You can find it here:

https://wiki.php.net/rfc/closure-optimizations

Regards,
Ilija

[1] https://externals.io/message/129825

Claude Pache

213 days ago

> Le 31 janv. 2026 à 00:43, Ilija Tovilo <tovilo.ilija@gmail.com> a écrit :
>
> ﻿Hi everyone
>
> A week ago, I sent an e-mail to internals regarding two closure
> optimizations with some subtle BC breaks. [1] While nobody objected, I
> decided to create a short RFC anyway to avoid any possible controversy
> due to the BC breaks. You can find it here:
>
> https://wiki.php.net/rfc/closure-optimizations
>
> Regards,
> Ilija
>
> [1] https://externals.io/message/129825

Hi,

The examples of the RFC all use the `function () { }` construct. I guess it does also apply to closures constructed with `fn() =>` ?

—Claude

Ilija Tovilo

213 days ago

Hi Claude

On Sat, Jan 31, 2026 at 2:31 AM Claude Pache <claude.pache@gmail.com> wrote:

>
> > Le 31 janv. 2026 à 00:43, Ilija Tovilo <tovilo.ilija@gmail.com> a écrit :
> >
> > https://wiki.php.net/rfc/closure-optimizations
>
> The examples of the RFC all use the `function () { }` construct. I guess it does also apply to closures constructed with `fn() =>` ?

Yes, the same applies to arrow functions. I clarified in the text and
added a short example.

Ilija

Bob Weinand

213 days ago

Hey Ilija,

On 31.1.2026 00:40:05, Ilija Tovilo wrote:

> Hi everyone
>
> A week ago, I sent an e-mail to internals regarding two closure
> optimizations with some subtle BC breaks. [1] While nobody objected, I
> decided to create a short RFC anyway to avoid any possible controversy
> due to the BC breaks. You can find it here:
>
> https://wiki.php.net/rfc/closure-optimizations
>
> Regards,
> Ilija
>
> [1]https://externals.io/message/129825

I'm a bit disappointed that you felt necessary to introduce bureaucracy
for a straightforward very minor BC break. I don't like this something
to become necessary or expected in future. Sending that email was
completely sufficient.

I would like to encourage you to recognize that and simply merge your
pull request.

Thanks,

Bob

Ilija Tovilo

213 days ago

Hi Bob

On Sat, Jan 31, 2026 at 4:59 AM Bob Weinand <bobwei9@hotmail.com> wrote:

>
> On 31.1.2026 00:40:05, Ilija Tovilo wrote:
>
> https://wiki.php.net/rfc/closure-optimizations
>
> I'm a bit disappointed that you felt necessary to introduce bureaucracy for a straightforward very minor BC break. I don't like this something to become necessary or expected in future. Sending that email was completely sufficient.
>
> I would like to encourage you to recognize that and simply merge your pull request.

I agree that the BC break is fairly minimal. What made me decide to
create an RFC after all is highlighted here:

> ReflectionFunction::getClosureThis() will now return NULL for closures that are inferred as static. This might be slightly surprising, given static inference does not work 100% reliably, limited by the rules previously described.

ReflectionFunction::getClosureThis() will work as long as the closure
uses $this, but it will also work if it calls static methods. Once you
remove the static call, it will break. Now, I don't think
ReflectionFunction::getClosureThis() is something many people rely on,
nor should they, but it is nonetheless surprising. I'd like to avoid
the situation where this is categorized as a bug that is effectively
impossible to solve without removing the optimization.

Ilija

Joerg Sowa

213 days ago

Hi Ilija,

Thank you for this improvement. If I understand correctly, one of the
predicted BC changes will fix one of the issues with unit test comparisons.

The sebastianbergmann/comparator library cannot compare closures, because
each closure is in fact a different instance. With your change, this might
be resolved for static closures. So I see this is in fact very beneficial
for the unit testing.

https://github.com/sebastianbergmann/comparator/issues/129

Kind regards,
Jorg


On Sat, Jan 31, 2026 at 12:41 AM Ilija Tovilo <tovilo.ilija@gmail.com>
wrote:

Ilija Tovilo

189 days ago

Hi everyone

On Sat, Jan 31, 2026 at 12:40 AM Ilija Tovilo <tovilo.ilija@gmail.com> wrote:

>
> https://wiki.php.net/rfc/closure-optimizations

Given there hasn't been any recent feedback or change to the RFC, I
intend to start the vote on Friday.

Ilija