Php multisort with strftime

Question

Hello i have problem i want sort with strtotime row publishedAt but i get error

Warning: array_multisort(): Argument #3 is expected to be an array or a sort flag in D:\xampp\htdocs\test\page.php on line 6

$sql = "SELECT * FROM users";
$result = $conn->query($sql);
foreach ($result as $key => $part) {
       $sort[$key] = strtotime($part['publishedAt']);
    }
    array_multisort($sort, SORT_DESC, $videoList);

    for( $i= 0 ; $i <= count($videoList)-1 ; $i++ )
    {
        if(isset($videoList[$i]["videoId"])) {
            echo $videoList[$i]["videoId"];
        }
    }