Description:
------------
I was wondering why curl_errno() returned a 0 while beeing using with a curl_multi_init(). Not sure if this is a bug or if it's a documentation issue so I stated it first as an documentation issue.

It seems that the error is not populated into the resource. Only when I call curl_multi_info_read() then it gets populated into the resource.

References:

* https://bugs.php.net/bug.php?id=60660
* https://bugs.php.net/bug.php?id=33570
* https://bugs.php.net/bug.php?id=48304

Test script:
---------------
$handles = [];
$urls = [
    'https://www.google.com?v1',
    'https://wwwgooglecom?v2',
    'https://www.google.com?v3',
];

$mh = curl_multi_init();
foreach ($urls as $key => $value) {
    $handles[$key] = curl_init($value);
    curl_setopt($handles[$key], CURLOPT_HEADER, true);
    curl_setopt($handles[$key], CURLOPT_TIMEOUT, 10);
    curl_setopt($handles[$key], CURLOPT_RETURNTRANSFER, true);
    curl_multi_add_handle($mh, $handles[$key]);
}

do {
    $status = curl_multi_exec($mh, $running);
    curl_multi_select($mh);
} while ($running > 0 && $status === CURLM_OK);

// while ($result = curl_multi_info_read($mh)) {} // <<< uncomment this will give you the expected result

foreach($handles as $ch) {
    echo "Handle: " . curl_errno($ch) . PHP_EOL;
}

Expected result:
----------------
$ php test.php 
Result: (0) 
Result: (6) Could not resolve: wwwgooglecom (Domain name not found)
Result: (0) 


Actual result:
--------------
$ php test.php 
Result: (0) 
Result: (0) 
Result: (0)