使循环从最新的id开始

How can I make the loop start from latest id to first one?

    include 'config.php';

    $con->set_charset('utf8');
    $sql = "SELECT * FROM tablename";
    $names = mysqli_query($con,$sql);
    while($row = mysqli_fetch_array ($names)){

    //here will make loop start from first id
     }

Change your sql variable like this. This should work

$sql = "SELECT * FROM tablename ORDER BY `id` DESC";