<?php

use Symfony\Component\HttpClient\HttpClient;
use Symfony\Component\HttpClient\Exception\TransportException;
use Symfony\Component\Stopwatch\Stopwatch;

require_once __DIR__.'/vendor/autoload_runtime.php';

$client = HttpClient::create();
$stopwatch = new Stopwatch();

$stopwatch->start('not parallel');
try {
    $client->request('GET', 'http://10.255.255.1', ['timeout' => 5]);
} catch (TransportException) {
    echo ".";
}
echo "\n".$stopwatch->stop('not parallel')."\n";

$stopwatch->start('parallel');
$requests = [];
for ($i = 0; $i < 10; $i++) {
    $requests[] = $client->request('GET', 'http://10.255.255.1', ['timeout' => 5]);
}
foreach ($requests as $response) {
    try {
        $response->getContent();
    } catch (TransportException) {
        echo ".";
    }
}
echo "\n".$stopwatch->stop('parallel')."\n";

.
default/not parallel: 8.00 MiB - 5009 ms
..........
default/parallel: 8.00 MiB - 50053 ms