php - Form stops to pass data after user has logged in -

i want sort items on page , using form:

<form method="get" action="">             <label for="sort">sort items by</label>             <select id="sort" name="sort">                 <option value="">-</option>                 <option value="plth">price (low high)</option>                 <option value="phtl">price (high low)</option>                 <option value="naz">name (a-z)</option>                 <option value="nza">name (z-a)</option>             </select>             <input type="submit" name="sortsubmit" value="go >">         </form>  

after form has been processed, use sql statements retrieve items in desired order database:

if(isset($_get["sortsubmit"]) && $_get["sort"] == "plth") {                     $retrieve = "select * products id <= '9' order price asc";                 }                 elseif (isset($_get["sortsubmit"]) && $_get["sort"] == "phtl") {                     $retrieve = "select * products id <= '9' order price desc";                 }                 elseif (isset($_get["sortsubmit"]) && $_get["sort"] == "naz") {                     $retrieve = "select * products id <= '9' order name asc";                 }                 elseif (isset($_get["sortsubmit"]) && $_get["sort"] == "nza") {                     $retrieve = "select * products id <= '9' order name desc";                 } 

the problem is, working fine until user logs in. after user has logged in, stops working , cannot figure out why. testing echo statements found out form not passing data anymore. cant imagine how has sessions or cookies. ideas.

<form method="get" action="">      <label for="sort">sort items by</label>      <select id="sort" name="sort">          <option value="">-</option>          <option value="plth">price (low high)</option>          <option value="phtl">price (high low)</option>          <option value="naz">name (a-z)</option>          <option value="nza">name (z-a)</option>      </select>      <input type="submit" value="go">     </form>  

now if page called sort.php te form submit sort.php too.

this way, in header can read values this.

$sort = $_get['sort']; switch ($sort){ case "plth":  $retrieve = "select * products id <= '9' order price asc"; break; // other possible value andling here