How to Run Asynchronous Tasks with Swoole’s Task Workers in PHP

Swoole allows you to offload time‑consuming operations—such as broadcasting messages in a chat server or sending emails—from the main worker process by submitting them to a pool of task workers. The task() function is non‑blocking, returning immediately so the worker can continue handling new requests.

To use this feature you must configure the number of task workers with the task_worker_num setting and register the onTask and onFinish event callbacks on the server instance.

<?php
$serv = new Swoole\Server("127.0.0.1", 9501);
// Set the number of asynchronous task workers
$serv->set(array(
    'task_worker_num' => 4
));

// Callback executed in the worker process when data is received
$serv->on('receive', function($serv, $fd, $from_id, $data) {
    // Dispatch an asynchronous task
    $task_id = $serv->task($data);
    echo "Dispatch AsyncTask: id=$task_id
";
});

// Callback executed in a task worker process
$serv->on('task', function($serv, $task_id, $from_id, $data) {
    echo "New AsyncTask[id=$task_id]";
    // Return the result of the task
    $serv->finish("$data -> OK");
});

// Callback executed in the worker process when a task finishes
$serv->on('finish', function($serv, $task_id, $data) {
    echo "AsyncTask[$task_id] Finish: $data".PHP_EOL;
});

$serv->start();

The receive callback receives client data and immediately calls $serv->task($data) to hand the payload to a task worker. The task worker runs the onTask callback, processes the data, and calls $serv->finish() to send the result back. Finally, the onFinish callback runs in the original worker process, where you can handle the task’s outcome. Note that calling finish() is optional; a task can complete without returning a result.

After setting up the callbacks and starting the server with $serv->start(), the asynchronous task flow operates transparently, keeping the main request handling fast and responsive.