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Date: Thu, 22 Jan 2026 15:33:59 +0000 (GMT)
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>
cc: php internals <internals@lists.php.net>, 
    Arnaud Le Blanc <arnaud.lb@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Partial Function Application for instance of
 non-static methods ("$this")
In-Reply-To: <64953ec741a4c6609519e1878ad37b54@bastelstu.be>
Message-ID: <253ee811-0c1d-7eab-4c36-38607401aaf6@php.net>
References: <64953ec741a4c6609519e1878ad37b54@bastelstu.be>
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From: derick@php.net (Derick Rethans)

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On Thu, 22 Jan 2026, Tim D=C3=BCsterhus wrote:

> Arnaud and I would like to start discussion on our RFC =E2=80=9CPartial F=
unction
> Application for instance of non-static methods ("$this")=E2=80=9D which i=
s intended to
> round-off the Partial Function Application RFC that was accepted recently=
:
>=20
> https://wiki.php.net/rfc/partial_function_application_this

=09We propose allowing a named parameter $this: ? to be combined with the=
=20
=09=E2=80=9Cscope resolution operator=E2=80=9D syntax of referring to a met=
hod.

I can't say I am entirely sold on the syntax here =E2=80=94 starting with a=
 $=20
makes it look like a variable.

=09Since the $this: ? parameter does not refer to a parameter in=20
=09the underlying argument list and thus there is no ambiguity with=20
=09regard to positional parameters it may be placed at any position=20
=09of the parameter list=20

I think I would be keen on *requiring* this to be the **first** in the=20
argument list.

Although there is no ambiguity, I also can't see why you would want to=20
have it anywhere else.

And the RFC does acknowledge "instance methods which effectively carry=20
an implicit $this parameter that is provided on the left side of the ->=20
operator."

With both these two above comments, I think I would like to see a better=20
syntax =E2=80=94 but I am unsure if that's possible.

=09It may also not be used when partially applying an instance=20
=09method with a known object.

=09$c =3D $dateTime->format($this: ?, "c"); // Fatal error: Invalid use of =
$this placeholder

Can you explain (in the RFC) what you mean by "known object" =E2=80=94 I do=
n't=20
think the language on what this means is clear enough.

cheers,
Derick
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