(PHP 8 >= 8.1.0)
Fibers representam funções interrompíveis de pilha completa. Fibers podem ser suspensas de qualquer lugar na pilha de chamadas, pausando a execução dentro de Fiber até que Fiber seja retomada posteriormente.
Fibers pausam toda a pilha de execução, portanto, o chamador direto da função não precisa alterar a forma como invoca a função.
A execução pode ser interrompida em qualquer lugar na pilha de chamadas usando Fiber::suspend() (ou seja, a chamada para Fiber::suspend() pode estar em uma função profundamente aninhada ou nem mesmo existir).
Ao contrário dos Generators, cada Fiber tem sua própria pilha de chamadas, permitindo que sejam pausadas em chamadas de função profundamente aninhadas. Uma função que declara um ponto de interrupção (isto é, chamando Fiber::suspend()) não precisa alterar seu tipo de retorno, ao contrário de uma função que usa yield, que deve retornar uma instância de Generator.
Fibers podem ser suspensas em qualquer chamada de função, incluindo aquelas chamadas de dentro da VM PHP, como funções fornecidas para array_map() ou métodos chamados por foreach em um objeto Iterator.
Uma vez suspensa, a execução de Fiber pode ser retomada com qualquer valor usando Fiber::resume() ou lançando uma exceção na Fiber usando Fiber::throw(). O valor é retornado (ou exceção lançada) de Fiber::suspend().
Nota: Devido às limitações atuais, não é possível trocar Fibers no destruidor de um objeto.
Exemplo #1 Uso básico
<?php
$fiber = new Fiber(function (): void {
$value = Fiber::suspend('fiber');
echo "Value used to resume fiber: ", $value, PHP_EOL;
});
$value = $fiber->start();
echo "Value from fiber suspending: ", $value, PHP_EOL;
$fiber->resume('test');
?>O exemplo acima produzirá:
Value from fiber suspending: fiber Value used to resume fiber: test
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');
?>Here is a simple scheduler and thread pool that implements multithreading using fibers and tick functions in PHP 8.1 and returns the return value of each function in the pool in an array at the end.
Note that due to some bugs, you need to register a new tick function for each "thread". Remember to unregister all of them at the end.
The link bellow is the discussion on a bug that is going on right now (At the time of writing this). Note that based on the discussion, the ability to call Fiber::suspend() inside tick function may become forbidden in PHP 8.2+. But if the bug gets fixed, you can move register_tick_function() line to the top of the class, and this simple multithreading class in pure PHP code will work like a charm.
https://github.com/php/php-src/issues/8960
<?php
declare(ticks=1);
class Thread {
protected static $names = [];
protected static $fibers = [];
protected static $params = [];
public static function register(string|int $name, callable $callback, array $params)
{
self::$names[] = $name;
self::$fibers[] = new Fiber($callback);
self::$params[] = $params;
}
public static function run() {
$output = [];
while (self::$fibers) {
foreach (self::$fibers as $i => $fiber) {
try {
if (!$fiber->isStarted()) {
// Register a new tick function for scheduling this fiber
register_tick_function('Thread::scheduler');
$fiber->start(...self::$params[$i]);
} elseif ($fiber->isTerminated()) {
$output[self::$names[$i]] = $fiber->getReturn();
unset(self::$fibers[$i]);
} elseif ($fiber->isSuspended()) {
$fiber->resume();
}
} catch (Throwable $e) {
$output[self::$names[$i]] = $e;
}
}
}
return $output;
}
public static function scheduler () {
if(Fiber::getCurrent() === null) {
return;
}
// running Fiber::suspend() in this if condition will prevent an infinite loop!
if(count(self::$fibers) > 1)
{
Fiber::suspend();
}
}
}
?>
And here is an example code on how to use above Thread class:
<?php
// defining a non-blocking thread, so multiple calls will run in concurrent mode using above Thread class.
function thread (string $print, int $loop)
{
$i = $loop;
while ($i--){
echo $print;
}
return "Thread '{$print}' finished after printing '{$print}' for {$loop} times!";
}
// registering 6 Threads (A, B, C, D, E, and F)
foreach(range('A', 'F') as $c) {
Thread::register($c, 'thread', [$c, rand(5, 20)]);
}
// run threads and wait until execution finishes
$outputs = Thread::run();
// print outputs
echo PHP_EOL, '-------------- RETURN VALUES --------------', PHP_EOL;
print_r($outputs);
?>
The output will be something like this (but probably different):
ABCDEFABCDEFABCDEFABCDEFABCDEFABCEFABFABFABEBEFBEFEFEFAABEABEBEFBEFFAAAAAA
-------------- RETURN VALUES --------------
Array
(
[D] => Thread 'D' finished after printing 'D' for 5 times!
[C] => Thread 'C' finished after printing 'C' for 6 times!
[E] => Thread 'E' finished after printing 'E' for 15 times!
[B] => Thread 'B' finished after printing 'B' for 15 times!
[F] => Thread 'F' finished after printing 'F' for 15 times!
[A] => Thread 'A' finished after printing 'A' for 18 times!
)I think that in some cases it makes sense to convert a Fiber to a Generator (Coroutine) for convenience. In such cases, this code will be useful:
<?php
function fiber_to_coroutine(\Fiber $fiber): \Generator
{
$index = -1; // Note: Pre-increment is faster than post-increment.
$value = null;
// Allow an already running fiber.
if (!$fiber->isStarted()) {
$value = yield ++$index => $fiber->start();
}
// A Fiber without suspends should return the result immediately.
if (!$fiber->isTerminated()) {
while (true) {
$value = $fiber->resume($value);
// The last call to "resume()" moves the execution of the
// Fiber to the "return" stmt.
//
// So the "yield" is not needed. Skip this step and return
// the result.
if ($fiber->isTerminated()) {
break;
}
$value = yield ++$index => $value;
}
}
return $fiber->getReturn();
}
?>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);
?>Example of the same functionality showing what is the difference between Fiber and Generator
<?php
$gener = (function () use (&$gener): Generator {
$userfunc = function () use (&$gener) : Generator {
register_shutdown_function(function () use (&$gener) {
$gener->send('test');
});
return yield 'test';
};
$parm = yield from $userfunc();
echo "Value used to resume fiber: ", $parm, PHP_EOL;
})();
$res = $gener->current();
echo "Value from fiber suspending: ", $res, PHP_EOL;
?>
<?php
$fiber = new Fiber(function () use (&$fiber) : void {
$userfunc = function () use (&$fiber) : string {
register_shutdown_function(function () use (&$fiber) {
$fiber->resume('test');
});
return Fiber::suspend('fiber');
};
$parm = $userfunc();
echo "Value used to resume fiber: ", $parm, PHP_EOL;
});
$res = $fiber->start();
echo "Value from fiber suspending: ", $res, PHP_EOL;
?>TL;DR
The Thread class from Ali Madabi above has been eventually deprecated by the linked issue as relaying on tick functions for preemptive multi-threading simulation has been deemed "bad practice". Better ways were suggested for achieving some sort of multi-threading, such as: Revolt and AMP.
https://github.com/php/php-src/issues/8960#issuecomment-1184249445