Boost PHP Performance with Swow: Install, Coroutines, and Server Examples

What Is Swow?

Swow is a PHP extension that combines a minimal C core with mostly PHP code to enable high‑performance network programming. It offers seamless integration between PHP and the C kernel, giving developers powerful capabilities for building concurrent applications.

Key Features

Coroutine support

High performance

Fine‑grained control

Easy compatibility with existing PHP code

Installation

Require the package via Composer: composer require swow/swow Run the builder script: php vendor/bin/swow-builder Verify the installation: php --ri swow Successful output shows the extension is enabled and lists version, build date, and linked libraries.

Coroutine Basics

A coroutine (user‑space thread) is a lightweight, non‑preemptive concurrency primitive. Multiple coroutines run on a single OS thread, but only one coroutine executes at any moment. They can pause and resume by saving and restoring execution state.

Advantages of Coroutines

Lightweight

: Lower creation/destruction cost and memory usage than OS threads. No explicit locks: Single‑threaded execution avoids deadlocks and race conditions. Efficient context switches: Faster than thread switches, improving performance under high concurrency. Flexible scheduling: Programmers control when coroutines run, tailoring behavior to specific workloads.

Using Swow Coroutines

Run a coroutine with Swow\Coroutine::run:

Swow\Coroutine::run(static function(): void {
    echo 1;
    sleep(1);
});

Get the current coroutine object:

Swow\Coroutine::run(static function(): void {
    var_dump(\Swow\Coroutine::getCurrent());
});

Coroutine States

Swow defines three states: waiting: The coroutine is idle, either newly created or blocked on I/O. running: The coroutine is actively executing. dead: The coroutine has finished execution and its resources are released.

Example of inspecting a waiting coroutine:

$coroutine = Swow\Coroutine::run(static function(): void {
    \Swow\Coroutine::yield();
});
var_dump($coroutine);

Channel Communication

Channels provide a queue‑like mechanism for passing data between coroutines.

$channel = new \Swow\Channel();
Swow\Coroutine::run(static function() use ($channel): void {
    $channel->push(1);
});
Swow\Coroutine::run(function() use ($channel): void {
    var_dump($channel->pop());
});

Channels can also be used to handle signals, such as terminating on SIGINT (Ctrl+C):

$channel = new \Swow\Channel();
\Swow\Coroutine::run(static function() use ($channel): void {
    \Swow\Signal::wait(\Swow\Signal::INT);
    $channel->push("Terminated by SIGINT
");
});
// Consumer coroutine
\Swow\Coroutine::run(static function() use ($channel): void {
    while (true) {
        sleep(1);
    }
});
$timeout = 5;
try {
    echo $channel->pop($timeout * 1000);
} catch (\Swow\ChannelException $e) {
    echo sprintf("Timeout after %d seconds
", $timeout);
}

Quick HTTP Server with Swow

$server = new \Swow\Psr7\Server\Server();
$server->bind('0.0.0.0', 9503)->listen();
while (true) {
    $connection = $server->acceptConnection();
    \Swow\Coroutine::run(static function() use ($connection): void {
        try {
            while (true) {
                $request = $connection->recvHttpRequest();
                if ($request->getUri()->getPath() === '/') {
                    $connection->respond('22222');
                }
            }
        } catch (Throwable $e) {
            // handle error
        }
    });
}

Access http://127.0.0.1:9503 to see the response 22222.

Quick TCP Server with Swow

$server = new \Swow\Socket(\Swow\Socket::TYPE_TCP);
$server->bind('127.0.0.1', 9503)->listen();
while (true) {
    $connection = $server->accept();
    \Swow\Coroutine::run(static function() use ($connection): void {
        $buffer = new Swow\Buffer(Swow\Buffer::COMMON_SIZE);
        try {
            while (true) {
                $len = $connection->recv($buffer);
                if ($len === 0) {
                    break;
                }
                echo "No.{$connection->getFd()} say: \"" . addcslashes($buffer->toString(), "
") . "\"
";
                $connection->send($buffer);
            }
        } catch (Swow\SocketException $e) {
            echo "No.{$connection->getFd()} goaway! {$e->getMessage()}
";
        }
    });
}