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Date: Fri, 6 Feb 2026 17:43:29 +0100
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Subject: Re: [PHP-DEV] [RFC] Partial Function Application for instance of
 non-static methods ("$this")
To: Larry Garfield <larry@garfieldtech.com>,
 php internals <internals@lists.php.net>
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

On 1/22/26 17:41, Larry Garfield wrote:
> More spitballing on my previous reply:
> 
> class Test {
>    public function stuff(int $a) {}
> }
> 
> (Test)?->stuff(?);

As mentioned in the sibling mail, this is existing syntax and thus 
doesn't work.

> But if there's no partialing on the method side, it could get abbreviated to:
> 
> (?)->stuff(4);
> 
> Translates to:
> 
> fn(object $__this) => $__this->stuff(4);
> 
> Because we don't need to know the type at compile time, and a method-not-found error would still happen at runtime anyway if necessary.

By that argument you wouldn't need to type the argument as `object` 
either (calling methods on a non-object will throw) and the comparison 
would become:

     $c = (?)->stuff(4);
     $c = fn($o) => $o->stuff(4);

Keeping full type information is the main benefit of PFA over “just 
write a Closure”. Being able to reorder parameters as part of partial 
application is another explicit feature that would not be supported by 
that syntax.

> That would then be a lot easier to write in cases where you're just dropping a $this->stuff() call into a pipe chain but want to receive $this.

The use case for partially applying `$this` is in cases where you need a 
“function handle”, that's why the examples are ones where the resulting 
Closure is passed as a parameter to another function.

Within a pipe chain you would just use the regular `->` operator on the 
result of the previous step:

     $result = (trim($username)
         |> $repository->findBy(name: ?)
         )->getId();

It would also naturally support `?->` in case your repository returns 
`null` when the user cannot be found.

Best regards
Tim Düsterhus