curl_multi_the_correct_way.php

<?php
// ....
function processCurlMulti($curl_session_multi) {
  do {
    $mrc = curl_multi_exec($curl_session_multi, $n_running_channel);
  } while ($mrc == CURLM_CALL_MULTI_PERFORM || $n_running_channel > 0);

  $n_idle = 0;

  while ($mrc == CURLM_OK && $n_idle <= MAX_WAIT_CYCLES) {
    if (curl_multi_select($curl_session_multi) != -1) {
      $n_idle = 0;
      do {
        $mrc = curl_multi_exec($curl_session_multi, $n_running_channel);
      } while ($mrc == CURLM_CALL_MULTI_PERFORM || $n_running_channel > 0);
    } else {
      $n_idle++;
      usleep(250000);
    }
  }
  return $mrc;
}
// ....