SymfonyWorld Online 2022 Winter Edition

Fibers

Fibers overview

(PHP 8 >= 8.1.0)

Fibers represent full-stack, interruptible functions. Fibers may be suspended from anywhere in the call-stack, pausing execution within the fiber until the fiber is resumed at a later time.

Fibers pause the entire execution stack, so the direct caller of the function does not need to change how it invokes the function.

Execution may be interrupted anywhere in the call stack using Fiber::suspend() (that is, the call to Fiber::suspend() may be in a deeply nested function or not even exist at all).

Unlike stack-less Generators, each Fiber has its own call stack, allowing them to be paused within deeply nested function calls. A function declaring an interruption point (that is, calling Fiber::suspend()) need not change its return type, unlike a function using yield which must return a Generator instance.

Fibers can be suspended in any function call, including those called from within the PHP VM, such as functions provided to array_map() or methods called by foreach on an Iterator object.

Once suspended, execution of the fiber may be resumed with any value using Fiber::resume() or by throwing an exception into the fiber using Fiber::throw(). The value is returned (or exception thrown) from Fiber::suspend().

Note: Due to current limitations it is not possible to switch fibers in the destructor of an object.

Example #1 Basic usage

<?php
$fiber 
= new Fiber(function (): void {
   
$value Fiber::suspend('fiber');
   echo 
"Value used to resume fiber: "$valuePHP_EOL;
});

$value $fiber->start();

echo 
"Value from fiber suspending: "$valuePHP_EOL;

$fiber->resume('test');
?>

The above example will output:

Value from fiber suspending: fiber
Value used to resume fiber: test
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User Contributed Notes 2 notes

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6
user at csa dot es
1 month ago
Perhaps not using the same variable name everywhere will be a good idea

<?php
$fiber
= new Fiber(function (): void {
  
$parm = Fiber::suspend('fiber');
   echo
"Value used to resume fiber: ", $parm, PHP_EOL;
});

$res = $fiber->start();

echo
"Value from fiber suspending: ", $res, PHP_EOL;

$fiber->resume('test');
?>
up
0
maxpanchnko at gmail dot com
1 month ago
One of examples, how to make multi_curl faster twice (pseudocode) using Fibers:

<?php

$curlHandles
= [];
$urls = [
   
'https://example.com/1',
   
'https://example.com/2',
    ...
   
'https://example.com/1000',
];
$mh = curl_multi_init();
$mh_fiber = curl_multi_init();

$halfOfList = floor(count($urls) / 2);
foreach (
$urls as $index => $url) {
   
$ch = curl_init($url);
   
$curlHandles[] = $ch;

   
// half of urls will be run in background in fiber
   
$index > $halfOfList ? curl_multi_add_handle($mh_fiber, $ch) : curl_multi_add_handle($mh, $ch);
}

$fiber = new Fiber(function (CurlMultiHandle $mh) {
   
$still_running = null;
    do {
       
curl_multi_exec($mh, $still_running);
       
Fiber::suspend();
    } while (
$still_running);
});

// run curl multi exec in background while fiber is in suspend status
$fiber->start($mh_fiber);

$still_running = null;
do {
   
$status = curl_multi_exec($mh, $still_running);
} while (
$still_running);

do {
   
/**
     * at this moment curl in fiber already finished (maybe)
     * so we must refresh $still_running variable with one more cycle "do while" in fiber
     **/
   
$status_fiber = $fiber->resume();
} while (!
$fiber->isTerminated());

foreach (
$curlHandles as $index => $ch) {
   
$index > $halfOfList ? curl_multi_remove_handle($mh_fiber, $ch) : curl_multi_remove_handle($mh, $ch);
}
curl_multi_close($mh);
curl_multi_close($mh_fiber);
?>
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