Here's an easier to follow example, From : http://arguments.callee.info/2010/02/21/multiple-curl-requests-with-php/

// build the individual requests, but do not execute them
$ch_1 = curl_init('http://webservice.one.com/');
$ch_2 = curl_init('http://webservice.two.com/');
curl_setopt($ch_1, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch_2, CURLOPT_RETURNTRANSFER, true);
  
// build the multi-curl handle, adding both $ch
$mh = curl_multi_init();
curl_multi_add_handle($mh, $ch_1);
curl_multi_add_handle($mh, $ch_2);
  
// execute all queries simultaneously, and continue when all are complete
  $running = null;
  do {
    curl_multi_exec($mh, $running);
  } while ($running);

//close the handles
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
  
// all of our requests are done, we can now access the results
$response_1 = curl_multi_getcontent($ch_1);
$response_2 = curl_multi_getcontent($ch_2);
echo "$response_1 $response_2"; // output results

According to https://bugs.php.net/bug.php?id=61141:

On Windows setups using libcurl version 7.24 or later (which seems to correspond to PHP 5.3.10 or later), you may find that curl_multi_select() always returns -1, causing the example code in the documentation to timeout. This is, apparently, not strictly a bug: according to the libcurl documentation, you should add your own sleep if curl_multi_select returns -1.

Therefore, in order to work correctly on Windows for PHP 5.3.10+, the second loop in the example code should look something like the following:

<?php
while ($active && $mrc == CURLM_OK) {
    if (curl_multi_select($mh) == -1) {
        usleep(100);
    }
    do {
        $mrc = curl_multi_exec($mh, $active);
    } while ($mrc == CURLM_CALL_MULTI_PERFORM);
}
?>

One of the URLs used in the first example on this page (lxr.php.net) now gives a proxy error.

If you're using this first script example, replace with a different URL.