Codeigniter的ajax函数

Question

I have a problem with an ajax function. I want to upload a CSV file and send it to the database. When I send it it goes into the function until "importing" and nothing else ... I have been blocking for quite some time so I hope you can help me.

this is the function in my view :

<script>

$(document).ready(function(){


    $('#import_csv').on('submit', function(event){
        event.preventDefault();
        $.ajax({
            url:"<?php echo base_url(); ?>Controller_diseaseTree/import",
            method:"POST",
            data:new FormData(this),
            contentType:false,
            cache:false,
            processData:false,
            beforeSend:function(){
                $('#import_csv_btn').html('Importing...');
            },

            success:function(data)
            {
                $('#import_csv')[0].reset();
                $('#import_csv_btn').attr('disabled', false);
                $('#import_csv_btn').html('Import Done');
            }
        })
    });

});
</script>

Model is here :

<?php
class csv_import_model extends CI_Model
{

    public function __construct(){
        $this->load->database();
    }


    function insert($data)
    {
        $this->db->insert_batch('durian_database.disease_tree', $data);
    }
}

Controller is here :

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Controller_diseaseTree extends CI_Controller {


    public function __construct()
    {
        parent::__construct();
        $this->load->helper('url');
        $this->load->model('diseaseTree_model');
        $this->load->model('typeOfDisease_model');
        $this->load->model('csv_import_model');
        $this->load->library('csvimport');


    }

    public function index()
    {
        if ($this->session->userdata('login') != FALSE){
            $data['navbar']  = 'user_navbar.php';
        } else {
            $data['navbar'] = 'navbar.php';
        }

        $login = $this->session->userdata('login');

        $this->load->vars($data);

        $diseaseTree_all = $this->diseaseTree_model->get_diseaseTree($login);

        $this->load->view('diseaseTree', compact('diseaseTree_all'));

    }

    public function TypeOfDisease(){

        if ($this->session->userdata('login') != FALSE){
            $data['navbar']  = 'user_navbar.php';
        } else {
            $data['navbar'] = 'navbar.php';
        }

        $this->load->vars($data);

        $TypeOfDisease = $this->typeOfDisease_model->get_TypeOfDisease();

        $this->load->view('typeOfDisease', compact('TypeOfDisease'));
    }

    public function delete_tree($tree_id)
    {
        $this->diseaseTree_model->delete_tree($tree_id, $this->session->userdata('login'));
        redirect("Controller_diseaseTree", "refresh");
    }


    function import()
    {
        if ($this->session->userdata('login') != FALSE){
            $data['navbar']  = 'user_navbar.php';
        } else {
            $data['navbar'] = 'navbar.php';
        }

        $file_data = $this->csvimport->get_array($_FILES["csv_file"]["tmp_name"]);
        foreach($file_data as $row)
        {
            $data[] = array(
                'user_login'    =>  $row["user_login"],
                'tree_number'       =>  $row["tree_number"],
                'longitude'         =>  $row["longitude"],
                'latitude'          =>  $row["latitude"],
                'area'          =>  $row["area"]

            );
        }

        $this->load->vars($data);
        $this->csv_import_model->insert($data);
    }


}

?>