hello i haven an error abour ajax post success. after the success function i added code for lookin for errors

...     
else if (exception === 'parsererror') {
  alert('Requested JSON parse failed.');
...

on my php code:

echo json_encode(array('msg' => $msg, 'myClass' => $class));

returns back after my function. i checked in firebug and it returns like, response like {"msg":"Kayd\u0131n\u0131z Ba\u015far\u0131l\u0131","myClass":"alert alert-success"} html like {"msg":"Kayd\u0131n\u0131z Ba\u015far\u0131l\u0131","myClass":"alert alert-success"}

there is no json tab on firebug and on my ajax code if i comment the dataType: "json", my success function is working but i cant get the response.msg or response.myClass, if i dont comment it, success function is not working, here is the ajax code

$.ajax({
  type: "POST",
  url: "index.php?page=addItem&action=addItem&edit=true", 
  data: dataString,
  success: function(response) {
        $("#message").html(response.msg);
        $("#message").addClass(response.myClass);
        $("#itemForm").fadeOut("slow");
        window.setTimeout('location.href = "index.php?page=addItem"', 1000); 
    }   
 });