pagination and drop down session

[Mickie D]

I have successfully setup pagination for my new modification, which gets the information from the database then limits the results to 10 items per page.

The only trouble is that I would now like to sort the items by different values, but I am not sure how sessions work in the respect do I need to add a column to the MySQL database or just setup a session variable?

This is my code:

PHP Code:

        $orderby = $vbulletin->input->clean_gpc('p', 'orderby', TYPE_NOTRIM);

        if(isset($orderby) ){

            switch ($orderby){
            case "1":    $order = "file_fullsize";     /*$sel_full = "selected='selected'";*/    break;
            case "2":    $order = "file_timestamp";    /*$sel_time = "selected='selected'";*/    break;
            case "3":    $order = "file_name";        /*$sel_name = "selected='selected'";*/    break;
            default:    $order = "file_fullsize";    
            } 
        }
        
        $dir = '/temp/'.$vbulletin->userinfo['username'] . "/";
        $dirsql = $vbulletin->db->query_read("SELECT * FROM " . TABLE_PREFIX . "web WHERE file_userid = '$r1' ORDER BY $order DESC LIMIT $limitlower, $perpage"); 


Code for the dropdown

PHP Code:

<form id="form1" name="form1" method="post" action="web.php">
<select name="orderby">
  <option value="1" name="file_fullsize">File Size</option>
  <option value="2" name="file_timestamp">File Added</option>
  <option value="3" name="file_name">File Name</option>
</select>  

<input type="submit" />
</form> 


This works great for page one of the pagination but because the pagination changes pages it just defaults the switch on any other page

file_fullsize

I guess that i need to store the drop down orderby variable across the pagination?

Thank you for any help
Mick