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Date: Thu, 23 Oct 2025 09:43:17 +0200
To: "Edmond Dantes" <edmond.ht@gmail.com>
Cc: "Aaron Piotrowski" <aaron@trowski.com>,
 "PHP Internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] PHP True Async RFC Stage 4
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From: rob@bottled.codes ("Rob Landers")

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On Thu, Oct 23, 2025, at 08:41, Edmond Dantes wrote:
> Hi
>=20
> > Assuming an awaitable is idempotent (such as the result of a corouti=
ne), this is an infinite loop. There=E2=80=99s a 99.9% chance that=E2=80=
=99s unintended, which is part of the point of static analysis.
>=20
> ```php
> foreach(($next =3D await($awaitable)) as $value) { }
> ```
>=20
> executed as:
> 1. await($awaitable) - will return some value
> 2. foreach got this value
> 3. If the value has a valid interface, then foreach will iterate over =
it.
>=20
> await($awaitable) -
>=20
> It always returns only one value because under the hood it works like =
this:
>=20
> ```
> function await(awaitable):
>     # 1) Create a waker for the current coroutine
>     waker =3D Waker(current_coroutine)
>=20
>     # 2) Register an event handler inside the awaitable
>     handler =3D function(result, error):
>         waker.set_result(result, error)
>         awaitable.remove_handler(handler) # detach
>         Scheduler.enqueue(waker.coroutine)
>=20
>     awaitable.add_handler(handler)
>=20
>     try:
>         # 3) Suspend the current coroutine until resumed
>         Scheduler.suspend(current_coroutine)
>=20
>         # 4) When the waker is triggered, return the stored result
>         return waker.get_result()
>=20
>     finally:
>         # 5) Destroy/cleanup the waker object
>         waker.dispose()                  # release buffers/slots
> ```
>=20
> > The RFC says that for coroutines, but not Awaitable. It is undefined.
> Sorry I can=E2=80=99t understand the meaning of this.
>=20
> Thanks, Ed

Nowhere in the RFC does it explain how await() applies to the Awaitable =
interface, it only specifies it in the context of a coroutine.

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title></head><body><div><br></div><d=
iv><br></div><div>On Thu, Oct 23, 2025, at 08:41, Edmond Dantes wrote:</=
div><blockquote type=3D"cite" id=3D"qt" style=3D""><div>Hi</div><div><br=
></div><div>&gt; Assuming an awaitable is idempotent (such as the result=
 of a coroutine), this is an infinite loop. There=E2=80=99s a 99.9% chan=
ce that=E2=80=99s unintended, which is part of the point of static analy=
sis.</div><div><br></div><div>```php</div><div>foreach(($next =3D await(=
$awaitable)) as $value) { }</div><div>```</div><div><br></div><div>execu=
ted as:</div><div>1. await($awaitable) - will return some value</div><di=
v>2. foreach got this value</div><div>3. If the value has a valid interf=
ace, then foreach will iterate over it.</div><div><br></div><div>await($=
awaitable) -</div><div><br></div><div>It always returns only one value b=
ecause under the hood it works like this:</div><div><br></div><div>```</=
div><div>function await(awaitable):</div><div>&nbsp;&nbsp;&nbsp; # 1) Cr=
eate a waker for the current coroutine</div><div>&nbsp;&nbsp;&nbsp; wake=
r =3D Waker(current_coroutine)</div><div><br></div><div>&nbsp;&nbsp;&nbs=
p; # 2) Register an event handler inside the awaitable</div><div>&nbsp;&=
nbsp;&nbsp; handler =3D function(result, error):</div><div>&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href=3D"http://waker.set">waker.se=
t</a>_result(result, error)</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;<a href=3D"http://awaitable.remove">awaitable.remove</a>_h=
andler(handler) # detach</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;<a href=3D"http://Scheduler.enqueue">Scheduler.enqueue</a>(<a=
 href=3D"http://waker.coroutine">waker.coroutine</a>)</div><div><br></di=
v><div>&nbsp;&nbsp;&nbsp;&nbsp;<a href=3D"http://awaitable.add">awaitabl=
e.add</a>_handler(handler)</div><div><br></div><div>&nbsp;&nbsp;&nbsp; t=
ry:</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; # 3) Suspend th=
e current coroutine until resumed</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;<a href=3D"http://Scheduler.suspend">Scheduler.suspe=
nd</a>(current_coroutine)</div><div><br></div><div>&nbsp;&nbsp;&nbsp;&nb=
sp;&nbsp;&nbsp;&nbsp; # 4) When the waker is triggered, return the store=
d result</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return&nbs=
p;<a href=3D"http://waker.get">waker.get</a>_result()</div><div><br></di=
v><div>&nbsp;&nbsp;&nbsp; finally:</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nb=
sp;&nbsp;&nbsp; # 5) Destroy/cleanup the waker object</div><div>&nbsp;&n=
bsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href=3D"http://waker.dispose"=
>waker.dispose</a>()&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; # release buffers/slo=
ts</div><div>```</div><div><br></div><div>&gt; The RFC says that for cor=
outines, but not Awaitable. It is undefined.</div><div>Sorry I can=E2=80=
=99t understand the meaning of this.</div><div><br></div><div>Thanks, Ed=
<br></div></blockquote><div><br></div><div>Nowhere in the RFC does it ex=
plain how await() applies to the Awaitable interface, it only specifies =
it in the context of a coroutine.</div><div><br></div><div id=3D"sig1212=
29152">=E2=80=94 Rob</div></body></html>
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