javascript - Codeigniter with ajax: success function not working

I have a problem with success function in my $.ajax function

in javascript file:

$("#country select").change(function () { 
            var country_value = $(this).val(); 
            $.ajax({
                url:base_url + "Search_controller/testing_controller", 
                method: 'post',
                data: {country_val: country_value },
                dataType: 'json',
                success: function(data){

                    console.log('done : ' + data);  
                },
                   error: function (reponse) {
                console.log('Problem with ajax');
                }

            });

my Controller function

   
class Search_controller extends CI_Controller{

    public function index(){

    }



    public function testing_controller(){
        $data ="statessssssss";
        echo json_encode($data);
    }

  }
?>

**

The Problem is the codes do nothing, i don't know what the problem
Always return to me in Browser log 'Problem with ajax'

**

Answer

I find the solution is because of CSRF security

$("#country select").change(function () { 
             var country_value= $(this).val(); 
             var data = { /* params  */
                    "country": country_value,
                     "state": '001'
                };
              data[csfr_token_name] = $.cookie(csfr_cookie_name);
            $.ajax({

                url:base_url + "Search_controller/testing_controller", 
                method: 'post',
                data: data,
                dataType: 'json',
                success: function(data){
                    console.log('done : ' + data);  
                },
                   error: function (reponse) {
                console.log('Problem with ajax');
                }


            });

This Code Working