Description:
------------
cURL resources returned by curl_multi_info_read() aren't usables with curl_errno() or curl_errno(). When an error occurs with these resources, the "handle" returned doesn't behave as a single handle.
I've created a draft PR with a test exposing the problem: https://github.com/php/php-src/pull/4075

Test script:
---------------
$urls = array(
   'http://nonexistent.tld',
);

$mh = curl_multi_init();

foreach ($urls as $i => $url) {
    $conn[$i] = curl_init($url);
    curl_multi_add_handle($mh, $conn[$i]);
}

do {
    $status = curl_multi_exec($mh, $active);
    $info = curl_multi_info_read($mh);
    if (false !== $info) {
        echo $info['result']."\n";
        echo curl_errno($info['handle'])."\n";
        echo curl_error($info['handle'])."\n";
    }
} while ($status === CURLM_CALL_MULTI_PERFORM || $active);

foreach ($urls as $i => $url) {
    curl_close($conn[$i]);
}

curl_multi_close($mh);

Expected result:
----------------
6
6
Could not resolve host: nonexistent.tld

Actual result:
--------------
6
0