Channel::send

(PHP 8.6+, True Async 1.0)

public Channel::send(mixed $value, ?Completable $cancellationToken = null): void

Sends a value to the channel. This is a blocking operation — the current coroutine is suspended if the channel cannot accept the value immediately.

For a rendezvous channel (capacity = 0), the sender waits until another coroutine calls recv(). For a buffered channel, the sender waits only when the buffer is full.

Parameters

value: The value to send. Can be of any type.
cancellationToken: A cancellation token (Completable) that allows cancelling the wait on any condition. null — wait indefinitely (default). When the token completes, the operation is cancelled and a CancelledException is thrown. To limit by time, you can use Async\timeout().

Errors

Throws Async\ChannelException if the channel is closed.
Throws Async\CancelledException if the cancellation token has been completed.

Examples

Example #1 Sending values to a channel

<?php

use Async\Channel;

$channel = new Channel(1);

spawn(function() use ($channel) {
    $channel->send('first');  // placed in the buffer
    $channel->send('second'); // waits for space to free up
    $channel->close();
});

spawn(function() use ($channel) {
    echo $channel->recv() . "\n"; // "first"
    echo $channel->recv() . "\n"; // "second"
});

Example #2 Sending with a timeout

<?php

use Async\Channel;

$channel = new Channel(0); // rendezvous

spawn(function() use ($channel) {
    try {
        $channel->send('data', Async\timeout(1000));
    } catch (\Async\CancelledException $e) {
        echo "Timeout: no one accepted the value within 1 second\n";
    }
});

Example #3 Sending with a custom cancellation token

<?php

use Async\Channel;
use Async\Future;

$channel = new Channel(0);
$cancel = new Future();

spawn(function() use ($channel, $cancel) {
    try {
        $channel->send('data', $cancel);
    } catch (\Async\CancelledException $e) {
        echo "Send cancelled\n";
    }
});

// Cancel the operation from another coroutine
spawn(function() use ($cancel) {
    Async\delay(500);
    $cancel->complete(null);
});

Documentation