A simple event loop with Fibers (PHP 8 >= 8.1.0)

eventloop.php

<?php

// a simple event loop with Fibers (PHP 8 >= 8.1.0)
// in a style slightly inspired by Python's asyncio

// this will not immediately increase the throughput of your code
// since the functions are still executed sequentially in the event loop

// unless you can combine it with a non-blocking stream/socket
// to create the impression of io parallelism


class Loop
{
    // defered tasks
    public static $tasks = [];

    public static function createTask($coro)
    {
        $fiber = new Fiber(function () use ($coro) {
            // defer
            Fiber::suspend();
            return $coro();
        });
        $fiber->start();

        self::$tasks[] = $fiber;
        return $fiber;
    }

    public static function await($fiber)
    {
        while (!$fiber->isTerminated()) {
            // yield the current task until an awaited task is done
            Fiber::suspend();
        }

        return $fiber->getReturn();
    }

    public static function run($coro = null)
    {
        // optionally create a main task
        if (is_callable($coro)) {
            self::createTask($coro);
        }

        // event loop
        while (self::$tasks) {
            $fiber = array_shift(self::$tasks);

            if ($fiber->isSuspended() && !$fiber->isTerminated()) {
                // execute defered tasks
                $fiber->resume();
            }

            if (!$fiber->isTerminated()) {
                // reschedule
                self::$tasks[] = $fiber;
            }
        }
    }
}


// coroutines
$coro1 = function () {
    return 'Task 1' . PHP_EOL;
};

$coro2 = function () {
    return 'Task 2' . PHP_EOL;
};

// tasks
$task1 = Loop::createTask($coro1);
$task2 = Loop::createTask($coro2);

$main = function () use ($task1, $task2) {
    echo Loop::await($task2);
    echo Loop::await($task1);

    echo 'Main task', PHP_EOL;
};


echo 'Before event loop', PHP_EOL;
var_dump(Loop::$tasks);

// run the event loop
Loop::run($main);

echo 'After event loop', PHP_EOL;
var_dump(Loop::$tasks);