Description:
------------
A cURL ressource seem to be not closed correctly after using it with curl_multi_exec. According to this answer on stackoverflow http://stackoverflow.com/a/23007037/363323 the handle should be removed since the internal counter should be 0 after curl_multi_remove_handle and curl_close should do the rest...

Test script:
---------------
        $ch1 = curl_init();
        $ch2 = curl_init();

        curl_setopt($ch1, CURLOPT_URL, 'http://lxr.php.net/');
        curl_setopt($ch1, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch2, CURLOPT_URL, 'http://www.php.net/');
        curl_setopt($ch2, CURLOPT_RETURNTRANSFER, 1);

        $cmh = curl_multi_init();
        curl_multi_add_handle($cmh, $ch1);
        curl_multi_add_handle($cmh, $ch2);
        
        $status = curl_multi_exec($cmh, $active);

        $innerSleepInt = $outerSleepInt = 1;
        while ($active && ($status === CURLM_OK || $status === CURLM_CALL_MULTI_PERFORM)) {
            usleep((int)$outerSleepInt);
            $outerSleepInt = (int) max(1, $outerSleepInt * 1.1);
            $multiSelect = curl_multi_select($cmh, 0);
            /* @see https://bugs.php.net/bug.php?id=63411 */
            if ($multiSelect === -1) {
                usleep(100000);
            }

            /* @see https://curl.haxx.se/libcurl/c/libcurl-errors.html */
            if ($multiSelect >= CURLM_CALL_MULTI_PERFORM) {
                do {
                    $status = curl_multi_exec($cmh, $active);
                    usleep((int) $innerSleepInt);
                    $innerSleepInt = (int) max(1, $innerSleepInt * 1.1);
                } while ($status === CURLM_CALL_MULTI_PERFORM);
                $innerSleepInt = 1;
            }

            while ($done = curl_multi_info_read($cmh)) {
                $ch = $done['handle'];
                curl_multi_getcontent($ch);
                curl_multi_remove_handle($cmh, $ch);
                curl_close($ch);
                echo is_resource($ch); // this should be return false
            }
        }