Channel::__construct

(PHP 8.6+, True Async 1.0)

public Channel::__construct(int $capacity = 0)

Creates a new channel for passing data between coroutines.

A channel is a synchronization primitive that allows coroutines to safely exchange data. The channel’s behavior depends on the $capacity parameter:

• capacity = 0 — rendezvous channel (unbuffered). The send() operation suspends the sender until another coroutine calls recv(). This ensures synchronous data transfer.
• capacity > 0 — buffered channel. The send() operation does not block as long as there is room in the buffer. When the buffer is full, the sender is suspended until space becomes available.

Parameters

capacity

The capacity of the channel’s internal buffer. 0 — rendezvous channel (default), send blocks until receive. Positive number — buffer size.

Examples

Example #1 Rendezvous channel (unbuffered)

<?php

use Async\Channel;

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

spawn(function() use ($channel) {
    $channel->send('hello'); // suspends until someone calls recv()
    echo "Sent\n";
});

spawn(function() use ($channel) {
    $value = $channel->recv(); // receives 'hello', unblocks the sender
    echo "Received: $value\n";
});

Example #2 Buffered channel

<?php

use Async\Channel;

$channel = new Channel(3); // buffer for 3 elements

spawn(function() use ($channel) {
    $channel->send(1); // does not block — buffer is empty
    $channel->send(2); // does not block — space available
    $channel->send(3); // does not block — last slot
    $channel->send(4); // suspends — buffer is full
});

See also

• Channel::send — Send a value to the channel
• Channel::recv — Receive a value from the channel
• Channel::capacity — Get the channel capacity
• Channel::close — Close the channel