使用PHP和GET方法排序？

Question

I'm trying to make a sorting, using links and GET method with them. I'll provide the code first and then explain what I'm trying to achieve. There could be a better way by using AJAX, and making it dynamic (I think?), but I want to start off with this first.

Code:

if(isset($_GET['order'])){$order = $_GET['order'];}else{$order = 0;}
if(isset($_GET['field'])){$order_field = $_GET['field'];}

switch($order)
{
    case 0: 
        $order_next = "DESC";
        break;
    case "DESC":
        $order_next = "ASC";
        break;
    case "ASC":
        $order_next = 0;
        break;
}

And later, in the HTML page I have this snippet:

<? 
if($order == 0)
{
    printf("<a href='admin.php?field=lastname&order=%s'>Last</a>
    ", $order_next);
}
else
{
    printf("<a href='admin.php?field=%s&order=%s'>Last</a><a class='sort_desc' href='admin.php?field=%s&order=%s'></a>
    ", $order_field, $order_next, $order_field, $order_next);
}
?>

Okay. I have a link Last, which should have 3 positions, default, DESC order, ASC order.
When I click on it once, it should send via GET method, that the field I clicked was "Lastname" field, and I need the next position (from default (without sorting) to next one (DESC in this case)). I can't quite catch the error on the code, or I don't understand something, doesn't the page reload properly or something? When I click the link, the $order and $order_field is read from the GET method, but nothing else happens. The switch doesn't work for some reason, and $order_next doesn't change into the new value, and there is only 1 link, instead of 2:
Default: Link "Last" DESC: Link "Last" + link with the triangle picture pointing down.

P.S: Sorry if I might not explain this too well, but I tried. Thank you for your time!

Answer 1

Change case 0: to case "0": and all will be good with the world :-)

This is because switch uses Loose Comparison

To understand why, just run this code and see the result:

var_dump("DESC" == 0);