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Date: Thu, 31 Aug 2017 22:28:36 +0800
To: internals@lists.php.net
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Subject: add Fiber (sackful coroutine) support
From: i@lvht.net (Haitao Lv)

Hi, All,

The generator has been introduced in PHP 5.5. And we can it pause a =
function execution.
With these feature, we can schedule multi io task in userland without =
blocking.

More details can be found at [Nikic].

And there is also some asynchronous frameworks like [AMP], which allow =
programer to=20
code like blocking, but run asynchronously.

However, like python's generator, lua's coroutine, javascript's =
async/await, php's
generator also is a stackless coroutine implementation. We cannot pause =
a function call
in it's sub function call. This is the reason that frameworks like [AMP] =
has many wrapper,
is hard to understand, and almost impossible to be used to implement =
real but complex system.

So I propose to introduce the sackful coroutine, aka Fiber, support for =
PHP. And the possible
API like this,

> <?php
> function foo($a)
> {
>   $b =3D await $a + 1;
>   echo $b;
> }
>=20
> function bar()
> {
>   foo();
> }
>=20
> $f =3D new Fiber(function($a) {
>   bar($a);
>   return 3;
> });
>=20
> $c =3D $f->resume(1);
> // 1 will be passed to lambda, then bar
> // bar call foo, and the **await** in foo paused this execution
> // and make the return value of resume as $a + 1
> // so $c is 2
>=20
> $c =3D $f->resume(3);
> // resume the execution by previous await, and the $b in foo
> // will be assigned a value of 3
> // so foo echo 3 and return and then the lambda return
> // and the resume got a return value of 3. so $c is 3.

So the Fiber API is a little like the Generator API, but is more simple =
yet powerful. So there
is no need to distinct $generator->current(), $generator->send(), and =
$generator->getReturn().

I made a more complex example at [FIREPHP].And I also make a [PR] for =
comment.

All comment are welcome. Thanks.

[Nikic] =
https://nikic.github.io/2012/12/22/Cooperative-multitasking-using-coroutin=
es-in-PHP.html
[AMP] http://amphp.org/
[FIREPHP] https://github.com/fiberphp/fiber-core/blob/master/app.php
[PR] https://github.com/php/php-src/pull/2723=