# [RFC][Discussion] Closure optimizations - Thread: https://externals.io/message/129957 - Original archive: https://news-web.php.net/php.internals/129957 - Started by Ilija Tovilo on 2026-01-30T23:40:05+00:00 - Messages: 7 - RFC: Closure optimizations (Implemented (PHP 8.6)) — https://externals.io/rfc/closure-optimizations.md - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · RFCs at https://externals.io/rfc.md · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #129957 — Ilija Tovilo — 2026-01-30T23:40:05+00:00 URL: https://externals.io/message/129957#129957 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 --- ## #129958 — Claude Pache — 2026-01-31T01:31:19+00:00 URL: https://externals.io/message/129957#129958 · In reply to: #129957 > Le 31 janv. 2026 à 00:43, Ilija Tovilo 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 --- ## #129960 — Bob Weinand — 2026-01-31T03:59:16+00:00 URL: https://externals.io/message/129957#129960 · In reply to: #129957 Hey Ilija, > 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 --- ## #129966 — Ilija Tovilo — 2026-01-31T16:32:48+00:00 URL: https://externals.io/message/129957#129966 · In reply to: #129960 Hi Bob > > > > 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 --- ## #129967 — Ilija Tovilo — 2026-01-31T16:35:44+00:00 URL: https://externals.io/message/129957#129967 · In reply to: #129958 Hi Claude > > > […] > > 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 --- ## #129969 — Jorg Sowa — 2026-01-31T17:54:23+00:00 URL: https://externals.io/message/129957#129969 · In reply to: #129957 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 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 --- ## #130147 — Ilija Tovilo — 2026-02-24T01:21:06+00:00 URL: https://externals.io/message/129957#130147 · In reply to: #129957 Hi everyone > > 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