DocumentationThreadChannel::__construct()

ThreadChannel::__construct ​

(PHP 8.6+, True Async 1.0)

php
public ThreadChannel::__construct(int $capacity = 0)

Creates a new thread-safe channel for passing data between OS threads.

ThreadChannel is the cross-thread counterpart of Channel. While Channel is designed for communication between coroutines within a single thread, ThreadChannel allows data to flow safely between separate OS threads — for example, between the main thread and a worker started with spawn_thread() or submitted to a ThreadPool.

The channel's behavior depends on the $capacity parameter:

  • capacity = 0 — unbuffered (synchronous) channel. send() blocks the calling thread until another thread calls recv(). This guarantees that the receiver is ready before the sender continues.
  • capacity > 0 — buffered channel. send() does not block as long as there is room in the buffer. When the buffer is full, the calling thread blocks until space becomes available.

All values transferred through the channel are deep-copied — the same serialization rules apply as with spawn_thread(). Objects that cannot be serialized (e.g. closures, resources, stdClass with references) will cause a ThreadTransferException.

Parameters ​

capacity : The capacity of the channel's internal buffer. 0 — unbuffered channel (default), send() blocks until a receiver is ready. Positive number — buffer size; send() blocks only when the buffer is full.

Examples ​

Example #1 Unbuffered channel between threads ​

php
<?php

use Async\ThreadChannel;
use function Async\spawn;
use function Async\spawn_thread;
use function Async\await;

spawn(function() {
    $channel = new ThreadChannel(); // capacity = 0

    $thread = spawn_thread(function() use ($channel) {
        $value = $channel->recv(); // blocks until main thread sends
        return "Worker received: $value";
    });

    $channel->send('hello'); // blocks until worker calls recv()
    echo await($thread), "\n";
});

Example #2 Buffered channel between threads ​

php
<?php

use Async\ThreadChannel;
use function Async\spawn;
use function Async\spawn_thread;
use function Async\await;

spawn(function() {
    $channel = new ThreadChannel(10); // buffer for 10 items

    $producer = spawn_thread(function() use ($channel) {
        for ($i = 1; $i <= 10; $i++) {
            $channel->send($i); // does not block until buffer is full
        }
        $channel->close();
    });

    $consumer = spawn_thread(function() use ($channel) {
        $results = [];
        while (!$channel->isClosed() || !$channel->isEmpty()) {
            try {
                $results[] = $channel->recv();
            } catch (\Async\ThreadChannelException) {
                break;
            }
        }
        return $results;
    });

    await($producer);
    $results = await($consumer);
    echo implode(', ', $results), "\n";
});

See also ​