The 12 Factor App: Port binding example with ReactPHP - http://slashnode.com/the-12-factor-php-app-part-2/

ReactDemo.php

<?php

include __DIR__.'/vendor/autoload.php';

$app = function ($request, $response) {
    $body = "" . time();
    
    $response->writeHead(200, ['Content-Type' => 'text/plain']);
    $response->end($body);
};

$loop = React\EventLoop\Factory::create();

$socket = new React\Socket\Server($loop);

$http = new React\Http\Server($socket, $loop);
$http->on('request', $app);

// set the port, start listening on the port
$socket->listen(8000);
$loop->run();

/* server running at localhost:8000 ... */