Question

Can anybody help me understand why are there two loops here?

 <?php
// create both cURL resources
$ch1 = curl_init();
$ch2 = curl_init();

// set URL and other appropriate options
curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net/");
curl_setopt($ch1, CURLOPT_HEADER, 0);
curl_setopt($ch2, CURLOPT_URL, "http://www.php.net/");
curl_setopt($ch2, CURLOPT_HEADER, 0);

//create the multiple cURL handle
$mh = curl_multi_init();

//add the two handles
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);

$active = null;
//execute the handles
do {
    $mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);

while ($active && $mrc == CURLM_OK) {
    if (curl_multi_select($mh) != -1) {
        do {
            $mrc = curl_multi_exec($mh, $active);
        } while ($mrc == CURLM_CALL_MULTI_PERFORM);
    }
}

//close the handles
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);

?>

Code is taken from http://php.net/manual/en/function.curl-multi-exec.php – the first example

Another issue is that the code strangely outputs everything to screen which never happened when using curl without the multi_exec feature. I needed to echo the content before, but not for this one, its blurts out everything without even asking.

Answer 1

There is no good explanation for that. It can indeed be moved into a single loop.

I believe this example code originates from demo code we did in plain C in the curl project that made that first call/loop to see if it should go on or not.

You can easily rewrite the code to use just a single loop.