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Date: Thu, 22 Jan 2026 11:18:28 -0600
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Subject: Re: [PHP-DEV] Closure optimizations
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From: larry@garfieldtech.com ("Larry Garfield")

On Thu, Jan 22, 2026, at 10:41 AM, Ilija Tovilo wrote:
> Hi Larry
>
> On Thu, Jan 22, 2026 at 5:03=E2=80=AFPM Larry Garfield <larry@garfield=
tech.com> wrote:
>>
>> On Wed, Jan 21, 2026, at 1:52 PM, Ilija Tovilo wrote:
>> >
>> > I've created a PR implementing two new optimizations for closures. =
[1]
>> > There are some theoretical BC breaks, so please let me know if any =
of
>> > them are of concern to you.
>> >
>> > Of note is that Closure::bind() and Closure::bindTo() usually throw
>> > when attempting to bind an object to a static closure. In my PR, th=
is
>> > is explicitly allowed only for closures that are inferred as static,
>> > but not those that are explicitly static.
>> >
>> >
>> > [1] https://github.com/php/php-src/pull/19941
>>
>> This all looks great, Ilija!  I am not concerned about the BC mention=
s, as they seem to be accurate anyway.
>>
>> My one question is about the bindTo() on an inferred static closure. =
 What purpose does that serve?  I'm assuming that anything that mentions=
 $this in its body won't be marked static, and if it doesn't have $this =
I don't get what value bindTo() would have.  What's the use case for mak=
ing an exception here?
>
> Oops, it seems I've left out some details I was meaning to add. The
> aim for allowing the passing of objects to Closure::bind[To]() is to
> retain BC when a closure can suddenly be inferred as static due to
> seemingly unrelated changes.
>
> As mentioned, the rules for when static can be inferred are slightly
> esoteric. For example, your code may be calling Foo::bar(), which
> _looks_ like a static call, but could actually be an instance
> grand-parent call (https://3v4l.org/uDi8W#v8.4.14). If you were to
> remove this ambiguous call, and the closure could now be inferred as
> static, it would be bad if existing Closure::bind[To]() calls would
> break because they provide an object. For this reason,
> Closure::bind[To]() will _accept but discard_ objects only for
> closures inferred as static.
>
> Ilija

Ah, so it's just a "don't break code that's already wrong but not harmfu=
lly so" feature.  I'm OK with that, but please add that to the RFC.

--Larry Garfield