Executing Multiple Curl Requests in Parallel With PHP and Curl_multi_exec

Let’s get one thing out in the open. Curl is sweet. It does it’s job very well, and I’m absoutely thrilled it exists.

If you’re using curl in your PHP app to make web requests, you’ve probably realized that by doing them one after the other, the total time of your request is the sum of all the requests put together. That’s lame.

Unfortunately using the curl_multi_exec is poorly documented in the PHP manual.

Let’s say that your app is hitting APIs from these servers:

Site Time
Google: .1s
Microsoft: .3s
rustyrazorblade.com: .5s

Your total time will be .9s, just for api calls.

By using curl_multi_exec, you can execute those requests in parallel, and you’ll only be limited by the slowest request, which is about .5 sec to rustyrazorblade in this case, assuming your download bandwidth is not slowing you down.

Sample code:

$nodes = array('http://www.google.com', 'http://www.microsoft.com', 'http://www.rustyrazorblade.com');
$node_count = count($nodes);

$curl_arr = array();
$master = curl_multi_init();

for($i = 0; $i < $node_count; $i++)
	$url =$nodes[$i];
	$curl_arr[$i] = curl_init($url);
	curl_setopt($curl_arr[$i], CURLOPT_RETURNTRANSFER, true);
	curl_multi_add_handle($master, $curl_arr[$i]);

do {
} while($running > 0);

echo "results: ";
for($i = 0; $i < $node_count; $i++)
	$results = curl_multi_getcontent  ( $curl_arr[$i]  );
	echo( $i . "\n" . $results . "\n");
echo 'done';

It’s really not documented on php.net how to use curl_multi_getcontent, so hopefully this helps someone.

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