If I run a standard cURL_multi_exec function (example below), I get all cURL handles requested at once. I would like to put a delay of 100ms between each request, is there a
Yes, this is possible. If you use the ParallelCurl library, you can much more easily add your 100ms delay with usleep(), as you can make a separate request to be added to the download queue.
for ($urls as $url) {
$pcurl->startRequest($url);
usleep(100000);
}