PHP Curl multi-exec requests not returning all data

I need some advice on debugging the code below please.

I'm feeding in Twitter user ids from $userIDArray. Because of Twitter limitations I have to break the calls up into batches of 100. So, if $userIDarray contains 512 users, I'm making 6 simultaneous calls using curl_multi_exec.

When I look at the return data the first batch of 100 responses is always fine, then after that I'm getting batches of only 0 and 1 results being returned. So, from 512 users I might only get return info for 120.

How do I find out what is happening with these calls please?

function getUserInfo() { global $userIDArray; global $counter; global $userInfoArray; $handleArray = array(); $requiredCalls = ceil($counter / 100); echo "Calls ".$requiredCalls."</br>"; $mh = curl_multi_init(); for($i = 0; $i < $requiredCalls; $i++) { $counterLow = $counter - 100; if($counterLow < 0) { $counterLow = 0; } //Take only 100 items $outputUIDArray = array_slice($userIDArray,$counterLow, $counter); //Implode array to string of user ids $uids = implode(",", $outputUIDArray); //echo "UIDs = ".$uids; $handle=curl_init(); curl_setopt($handle,CURLOPT_URL,'https://api.twitter.com/1/users/lookup.json?user_id='.$uids.'&include_entities=false'); curl_setopt($handle, CURLOPT_RETURNTRANSFER, 1); $handleArray[] = $handle; curl_multi_add_handle($mh,$handleArray[$i]); echo "Counter low ".$counterLow." Counter high ".$counter."</br>"; $counter -= 100; } $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); } } for($i = 0; $i < $requiredCalls; $i++) { //Get result $result = curl_multi_getcontent ($handleArray[$i]); //echo( $i . "\n" . $results . "\n"); $json_a=json_decode($result,true); echo count($json_a)."</br>"; //print_r($json_a); for($j = 0; $j < count($json_a); $j++) { $userInfoArray[] = $json_a[$j]; } var_dump(curl_multi_info_read($mh)); echo"</br>"; //close the handles curl_multi_remove_handle($mh, $handleArray[$i]); } curl_multi_close($mh); echo "Results in final array ".count($userInfoArray);}