how can i create a form that sort query asc or desc?

Hi I am trying to create a query that will sort the products display in ASC or DESC depending on the option the user selects from teh drop down.
I thought a switch statement would be a good option to achive this so this is how I have tried so far but fail miserable.

The switch statment

switch ($sortby) {
    case "ASC":
        	$args = array(
		's' => $_GET['s'],
		'post_type' => 'deals',
		'orderby' => 'title',
		'order' => 'ASC',
		'paged' => get_query_var('paged')
	);
    break;
    case "DESC":
                	$args = array(
		's' => $_GET['s'],
		'post_type' => 'deals',
		'orderby' => 'title',
		'order' => 'DESC',
		'paged' => get_query_var('paged')
	);
        break;
}

PHP:

The form

                                           <form name="myForm">
                                           		<select id="sortby"> 
                                                     <option value="ASC">ASC</option>
                                                      <option value="DESC">DESC</option>
                                                      <!-- <option value="pc">Postcode</option> -->
                                                </select>
                                           </form>

PHP:

Can someone help me out please

 

what's the problem? i don't get it

SELECT * FROM `table` WHERE `title` = 'hello world' ORDER BY `id` DESC

EDITED:

on a second look, change id="sortby" to name="sortby"

 

Hi this is what i am trying to achieve the clause WHERE= $variable bacause the drop down will be coming froma drop down.

      // get the post from the form (sortbyexpiry) and change the switch depending on the form value see form bellow
   switch ($_POST['location'])
   { 
       case "location": echo "<h3>location: $variable </h3>";
           $args = array(
                 's' => $_GET['s'],
                 'post_type' => 'deals',
                 'WHERE' => ' $variable',
                 'paged' => 'paged'
                );
           break;
   } 

PHP:

 

$variable = isset($_POST['sortby']) ? ($_POST['sortby'] == "DESC" ? "DESC" : "ASC") : "DESC";

is that it?