Channel::recv

(PHP 8.6+, True Async 1.0)

public Channel::recv(?Completable $cancellationToken = null): mixed

Receives the next value from the channel. This is a blocking operation — the current coroutine is suspended if no values are available in the channel.

If the channel is closed and the buffer is empty, a ChannelException is thrown. If the channel is closed but values remain in the buffer, they will be returned.

Parameters

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().

Return values

The next value from the channel (mixed).

Errors

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

Examples

Example #1 Receiving values from a channel

<?php

use Async\Channel;

$channel = new Channel(5);

spawn(function() use ($channel) {
    for ($i = 1; $i <= 5; $i++) {
        $channel->send($i);
    }
    $channel->close();
});

spawn(function() use ($channel) {
    try {
        while (true) {
            $value = $channel->recv();
            echo "Received: $value\n";
        }
    } catch (\Async\ChannelException) {
        echo "Channel closed and empty\n";
    }
});

Example #2 Receiving with a timeout

<?php

use Async\Channel;

$channel = new Channel();

spawn(function() use ($channel) {
    try {
        $value = $channel->recv(Async\timeout(2000));
        echo "Received: $value\n";
    } catch (\Async\CancelledException) {
        echo "No data received within 2 seconds\n";
    }
});

Example #3 Receiving with a custom cancellation token

<?php

use Async\Channel;
use Async\Future;

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

spawn(function() use ($channel, $cancel) {
    try {
        $value = $channel->recv($cancel);
        echo "Received: $value\n";
    } catch (\Async\CancelledException) {
        echo "Receive cancelled\n";
    }
});

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

Documentation