ComponentsChannel::recv

Channel::recv ​

(PHP 8.6+, True Async 1.0)

php
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 AsyncCancellation 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\AsyncCancellation if the cancellation token has been completed.

Examples ​

Example #1 Receiving values from a channel ​

php
<?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
<?php

use Async\Channel;

$channel = new Channel();

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

Example #3 Receiving with a custom cancellation token ​

php
<?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\AsyncCancellation) {
        echo "Receive cancelled\n";
    }
});

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

See also ​