ComponentsThreadChannel::close()

ThreadChannel::close ​

(PHP 8.6+, True Async 1.0)

php
public ThreadChannel::close(): void

Closes the channel. After closing:

  • Calling send() throws a ThreadChannelException.
  • Calling recv() continues to return values already in the buffer until it is drained. Once the buffer is empty, recv() throws a ThreadChannelException.
  • Any threads currently blocked in send() or recv() are unblocked and receive a ThreadChannelException.

Calling close() on an already closed channel is a no-op — it does not throw.

close() is the standard way to signal "end of stream" to the consuming side. The producer closes the channel after sending all items; the consumer reads until it catches ThreadChannelException.

close() itself is thread-safe and can be called from any thread.

Examples ​

Example #1 Producer closes after sending all items ​

php
<?php

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

spawn(function() {
    $channel = new ThreadChannel(10);

    $producer = spawn_thread(function() use ($channel) {
        foreach (['alpha', 'beta', 'gamma'] as $item) {
            $channel->send($item);
        }
        $channel->close(); // signals: no more data
    });

    $consumer = spawn_thread(function() use ($channel) {
        try {
            while (true) {
                echo $channel->recv(), "\n";
            }
        } catch (\Async\ThreadChannelException) {
            echo "Stream ended\n";
        }
    });

    await($producer);
    await($consumer);
});

Example #2 Close unblocks a waiting receiver ​

php
<?php

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

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

    // This thread will block in recv() waiting for a value
    $waiter = spawn_thread(function() use ($channel) {
        try {
            $channel->recv(); // blocks
        } catch (\Async\ThreadChannelException) {
            return "Unblocked by close()";
        }
    });

    // Close the channel from another thread — unblocks the waiter
    spawn_thread(function() use ($channel) {
        $channel->close();
    });

    echo await($waiter), "\n";
});

Example #3 Calling close() twice is safe ​

php
<?php

use Async\ThreadChannel;

$channel = new ThreadChannel(5);
$channel->close();
$channel->close(); // no-op, no exception thrown

echo $channel->isClosed() ? "closed" : "open"; // "closed"

See also ​