On the VG Tech blog today Espen Hovlandsdal has a quick tutorial showing you how to run cURL requests in parallel using the curl_multi_* functions included in PHP.
Ever had to request multiple HTTP-resources in your web application? Often, you need data from one request to be able to request the second - in this case there is little you can do but wait for the first to return. However, if the requests are not dependent on each other, you can use a pretty cool trick: curl_multi_*.
He first gives a single-threat example, showing how you might loop through a set of URLs to make the request and get the response. As an alternative, he shows the "multi" version right after. It sets up a "queue" of handles to different requests and executes them until they stop returning data. He also includes an example using the Guzzle HTTP client that makes it look cleaner and wraps some additional functionality around the requests.