$db = loader::db();
      $res = $db -> Execute('select description, isbn from btBookList where title = ?', array($title));
      $count = $res->RecordCount();
      if($count > 0)
      {
         $output = array();
            foreach($res as $row)
            {
               $output['isbn'] = $row['isbn'];
               $output['desc'] = $row['description'];
            }
         echo json_encode($output);
      }
      else
      {

{
"isbn":"9780553573404",
"desc":"The King needs a new hand and only Lord Eddard Stark will do. Winter is Coming"
}

$.get(url, data, function(response){
      if(response == 'invalid')
      {
            alert('no such book title');
      }
      else
      {
            alert(response.isbn);
      }
    })