Async/Await in PHP

async.php

<?php

function async(Closure $task): Closure
{
    static $resolved = [];

    if ( ! extension_loaded('pcntl') || ! extension_loaded('posix')) {
        return $task;
    }

    $id = uniqid();

    $path = implode(DIRECTORY_SEPARATOR, [
        sys_get_temp_dir(),
        'php_async_'.$id,
    ]);

    $pid = pcntl_fork();

    if ($pid === -1) {
        throw new RuntimeException('Failed to fork process.');
    }

    if ($pid === 0) {
        if (file_exists($path)) {
            unlink($path);
        }

        $result = $task($id);

        $pipe = fopen($path, 'w');

        fwrite($pipe, serialize($result));

        fclose($pipe);

        exit(0);
    }

    return function () use ($pid, $id, $path, &$resolved) {
        if (isset($resolved[$id])) {
            return $resolved[$id];
        }

        pcntl_waitpid($pid, $status);

        $pipe = fopen($path, 'r');

        $serialized = stream_get_contents($pipe);

        fclose($pipe);

        if (file_exists($path)) {
            unlink($path);
        }

        return $resolved[$id] ??= unserialize($serialized);
    };
}

function await(Closure|array $tasks): mixed
{
    if ( ! is_array($tasks)) {
        return $tasks();
    }

    return array_map(
        fn(Closure $task): mixed => $task(), $tasks,
    );
}