Asynchronous API calls using Guzzle

Guzzle.php

<?php
require 'vendor/autoload.php';

use GuzzleHttp\Client;
use GuzzleHttp\Pool;
use GuzzleHttp\Event\ErrorEvent;
use GuzzleHttp\Event\CompleteEvent;

$client = new Client();

$requests = array(
    "url1",
    "url2"
);

function raport() {
    echo "Do something after finishing all downloads";
}

$pool = new Pool($client, $requests);

$promise = $pool->send($client, $requests, [
        'complete' => function (CompleteEvent $event) {
            echo 'Completed request to ' . $event->getRequest()->getUrl() . "\n";
        },
        'error' => function (ErrorEvent $event) {
            echo 'Request failed: ' . $event->getRequest()->getUrl() . "<br/>";
            //echo $event->getException();
        }
]);


$promise->then(raport());