How to perform multiple Guzzle requests at the same time?

An update related to the new GuzzleHttp guzzlehttp/guzzle

Concurrent/parallel calls are now run through a few different methods including Promises.. Concurrent Requests

The old way of passing a array of RequestInterfaces will not work anymore.

See example here

    $newClient = new  \GuzzleHttp\Client(['base_uri' => $base]);
    foreach($documents->documents as $doc){

        $params = [
            'language' =>'eng',
            'text' => $doc->summary,
            'apikey' => $key
        ];

        $requestArr[$doc->reference] = $newClient->getAsync( '/1/api/sync/analyze/v1?' . http_build_query( $params) );
    }

    $time_start = microtime(true);
    $responses = \GuzzleHttp\Promise\unwrap($requestArr); //$newClient->send( $requestArr );
    $time_end = microtime(true);
    $this->get('logger')->error(' NewsPerf Dev: took ' . ($time_end - $time_start) );

Update: As suggested in comments and asked by @sankalp-tambe, you can also use a different approach to avoid that a set of concurrent request with a failure will not return all the responses.

While the options suggested with Pool is feasible i still prefer promises.

An example with promises is to use settle and and wait methods instead of unwrap.

The difference from the example above would be

$responses = \GuzzleHttp\Promise\settle($requestArr)->wait(); 

I have created a full example below for reference on how to handle the $responses too.

require __DIR__ . '/vendor/autoload.php';
use GuzzleHttp\Client as GuzzleClient;
use GuzzleHttp\Promise as GuzzlePromise;

$client = new GuzzleClient(['timeout' => 12.0]); // see how i set a timeout
$requestPromises = [];
$sitesArray = SiteEntity->getAll(); // returns an array with objects that contain a domain

foreach ($sitesArray as $site) {
    $requestPromises[$site->getDomain()] = $client->getAsync('http://' . $site->getDomain());
}

$results = GuzzlePromise\settle($requestPromises)->wait();

foreach ($results as $domain => $result) {
    $site = $sitesArray[$domain];
    $this->logger->info('Crawler FetchHomePages: domain check ' . $domain);

    if ($result['state'] === 'fulfilled') {
        $response = $result['value'];
        if ($response->getStatusCode() == 200) {
            $site->setHtml($response->getBody());
        } else {
            $site->setHtml($response->getStatusCode());
        }
    } else if ($result['state'] === 'rejected') { 
        // notice that if call fails guzzle returns is as state rejected with a reason.

        $site->setHtml('ERR: ' . $result['reason']);
    } else {
        $site->setHtml('ERR: unknown exception ');
        $this->logger->err('Crawler FetchHomePages: unknown fetch fail domain: ' . $domain);
    }

    $this->entityManager->persist($site); // this is a call to Doctrines entity manager
}

This example code was originally posted here.

From the docs: http://guzzle3.readthedocs.org/http-client/client.html#sending-requests-in-parallel

For an easy to use solution that returns a hash of request objects mapping to a response or error, see http://guzzle3.readthedocs.org/batching/batching.html#batching

Short example:

<?php

$client->send(array(
    $client->get('http://www.example.com/foo'),
    $client->get('http://www.example.com/baz'),
    $client->get('http://www.example.com/bar')
));