Here it is with comments…

// create an array containing the new order passed in
$order = split(’id’, $_GET['order']);
// drop the first item in the array since it is garbage
array_shift($order);

// loop through each item in the order array
foreach ($order as $val) {
    // create and execute query to update the “rank” or order of the host
    $sql = “UPDATE hosts SET rank=”.++$rank.” WHERE id=$val;”;
    mysql_query($sql);
}