Fibers

Übersicht über Fibers

(PHP 8 >= 8.1.0)

Fibers stellen unterbrechbare Funktionen dar, die den gesamten Aufrufstapel (Call-Stack) umfassen. Sie können an jeder Stelle des Aufrufstapels unterbrochen werden, wobei die Ausführung innerhalb der Fiber solange unterbrochen wird, bis die Fiber zu einem späteren Zeitpunkt fortgesetzt wird.

Fibers halten den gesamten Ausführungsstapel an, sodass der direkte Aufrufer der Funktion nicht ändern muss, wie er die Funktion aufruft.

Mit Fiber::suspend() kann die Ausführung an jeder Stelle im Aufrufstapel unterbrochen werden (d. h. der Aufruf von Fiber::suspend() kann in einer tief verschachtelten Funktion liegen oder auch gar nicht existieren).

Im Gegensatz zu einem Generator, der keinen Stapel hat, hat jede Fiber ihren eigenen Aufrufstapel, sodass sie innerhalb tief verschachtelter Funktionsaufrufe unterbrochen werden kann. Im Gegensatz zu einer Funktion, die yield verwendet und eine Generator-Instanz zurückgeben muss, muss eine Funktion, die einen Unterbrechungspunkt deklariert (d. h. Fiber::suspend() aufruft), ihren Rückgabetyp nicht ändern.

Fibers können beim Aufruf einer beliebigen Funktion unterbrochen werden. Dies gilt auch für Funktionen, die innerhalb der PHP-VM aufgerufen werden, z. B. Funktionen, die an array_map() übergeben werden oder Methoden eines Iterator-Objekts, die von foreach aufgerufen werden.

Sobald die Ausführung einer Fiber unterbrochen wurde, kann sie wieder aufgenommen werden, indem ein beliebiger Wert an Fiber::resume() übergeben wird oder indem Fiber::throw() verwendet wird, um eine Exception an die Fiber zu senden. Bei der Wiederaufnahme wird von Fiber::suspend() ein Wert zurückgegeben (oder es wird eine Exception ausgelöst).

Hinweis: Aufgrund der derzeitigen Beschränkungen ist es nicht möglich, Fibers im Destruktor eines Objekts zu schalten.

Beispiel #1 Grundlegende Verwendung

<?php
$fiber = new Fiber(function (): void {
   $value = Fiber::suspend('fiber');
   echo "Der Wert für die Wiederaufnahme der Fiber: ", $value, PHP_EOL;
});

$value = $fiber->start();

echo "Der Wert vom Unterbrechen der Fiber: ", $value, PHP_EOL;

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

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

Der Wert vom Unterbrechen der Fiber: fiber
Der Wert für die Wiederaufnahme der Fiber: test

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User Contributed Notes 6 notes

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user at csa dot es ¶

2 years 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');
?>

down

Ali Madadi ¶

2 years ago


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!
)

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nesk at xakep dot ru ¶

2 years ago


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();
}
?>

down

maxpanchnko at gmail dot com ¶

2 years 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);
?>

down

newuser ¶

2 years ago


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;
?>

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-12

dvohra09 at yahoo dot com ¶

2 years ago


Fiber::isRunning does not return a value
Sample
-------

<?php
 
 
$fiber = new Fiber(function (): void {
 $value = Fiber::suspend('suspend');
  
echo "Fiber is resumed with value: ", $value, "\n";

});
 
echo "Fiber not yet started.", "\n";

$value = $fiber->start(); 
 
echo "Fiber is started: ", $fiber->isStarted(), "\n";
echo "Fiber is suspended: ", $fiber->isSuspended(), "\n";

echo "Fiber is running: ", $fiber->isRunning(), "\n";
 
 echo "Fiber is suspended with value: ", $value, "\n";
 $fiber->resume('resume'); 

echo "Fiber is running: ", $fiber->isRunning(), "\n";

?>
Output
---

Fiber not yet started. Fiber is started: 1 Fiber is suspended: 1 Fiber is running: Fiber is suspended with value: suspend Fiber is resumed with value: resume Fiber is running:

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