composer.json

{
  "require": {
    "react/http": "*",
    "symfony/process": "*",
    "react/child-process": "*",
    "drift/react-functions": "*"
  }
}

request.php

<?php

$r = fopen('http://localhost:8080', 'r');
sleep(10);
fclose($r);

server.php

<?php

namespace App;

use Psr\Http\Message\ServerRequestInterface;
use React\EventLoop\Factory;
use React\EventLoop\TimerInterface;
use React\Http\Response;
use React\Http\Server;
use React\Stream\ThroughStream;
use function Drift\React\wait_for_stream_listeners;

require "vendor/autoload.php";

$loop = Factory::create();

$loop->addPeriodicTimer(1, function() {
    gc_collect_cycles();
    echo(memory_get_usage() . PHP_EOL);
});

$server = new Server(function (ServerRequestInterface $request) use ($loop) {
    $write = new ThroughStream();

    wait_for_stream_listeners($write, $loop, 1, 1)
        ->then(function ($write) use ($loop) {
            $pt = $loop->addPeriodicTimer(0.1, function (TimerInterface $timer) use ($write, $loop) {
                if (!$write->isWritable()) {
                    $loop->cancelTimer($timer);
                    return;
                }

                $res = $write->write(str_repeat('X', 10000));
                var_dump($res);
            });

            $loop->addTimer(10, function () use ($pt, $loop, $write) {
                $loop->cancelTimer($pt);
                $write->end();
            });
        });

    return new Response(
        200,
        array(
            'Content-Type' => 'text/plain',
        ),
        $write
    );
});

$socket = new \React\Socket\Server(8080, $loop);
$server->listen($socket);

$loop->run();