/!\ ATTENTION
/!\ Several of the non-downvoted notes on this page are using outdated info.
The CURLM_CALL_MULTI_PERFORM return code has been defunct since circa 2012, at least seven years ago.
Quoting the author of curl, from https://curl.haxx.se/mail/lib-2012-08/0042.html:
> CURLM_CALL_MULTI_PERFORM is deprecated and will never be returned, as documented.
> During the first decade or so of libcurl's multi interface, I never saw a single proper use of that feature. I did however see numerous mistakes and misunderstandings. That made me decide that the feature wasn't important or good enough, so since 7.20.0 CURLM_CALL_MULTI_PERFORM is no more.
Discovered all of this thanks to https://stackoverflow.com/q/19490837/3229684, which suggested the following replacement while loop:
<?php
do {
$mrc = curl_multi_exec($mc, $active);
} while ($active > 0);
?>
https://www.google.com/search?q=CURLM_CALL_MULTI_PERFORM <-- probably the most future-proof useful link I can put here