datatable server-side

---------------------------------------------
controller: Produk.php
---------------------------------------------
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Produk extends CI_Controller {
    public function __construct()
    {
        parent::__construct();
        $this->load->model('Admin/m_produk','produk');
    }

    public function index()
    {
        $this->load->helper('url');
        $this->load->view('Admin/produk/v_lihat');
    }

    public function ajax_list()
    {
        $list = $this->produk->get_datatables();
        $data = array();
        $no = $_POST['start'];
        foreach ($list as $produk) {
            $no++;
            $row = array();
            $row[] = $produk->nama_produk;
            $row[] = $produk->kat;
            $row[] = $produk->subkat;
            $row[] = $produk->supersubkat;

            //add html for action
            $row[] = '<a class="btn btn-sm btn-primary" href="javascript:void()" title="Edit" onclick="edit_produk('."'".$produk->id_produk."'".')"><i class="glyphicon glyphicon-pencil"></i> Edit</a>
                  <a class="btn btn-sm btn-danger" href="javascript:void()" title="Hapus" onclick="delete_produk('."'".$produk->id_produk."'".')"><i class="glyphicon glyphicon-trash"></i> Delete</a>';

            $data[] = $row;
        }

        $output = array(
                        "draw" => $_POST['draw'],
                        "recordsTotal" => $this->produk->count_all(),
                        "recordsFiltered" => $this->produk->count_filtered(),
                        "data" => $data,
                );
        //output to json format
        echo json_encode($output);
    }

---------------------------------------------
model: m_produk.php
---------------------------------------------
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class M_produk extends CI_Model {
    var $table = 'produk';
    //set column field database for order and search
    var $column = array('nama_produk','kat','subkat','supersubkat');
    var $order = array('id_produk' => 'desc'); // default order

    private function _get_datatables_query()
    {
        $this->db->from($this->table);

        $i = 0;

        foreach ($this->column as $item) // loop column
        {
            if($_POST['search']['value']) // if datatable send POST for search
            {
                if($i===0) // first loop
                {
                    $this->db->group_start(); // open bracket. query Where with OR clause better with bracket. because maybe can combine with other WHERE with AND.
                    $this->db->like($item, $_POST['search']['value']);
                }
                else
                {
                    $this->db->or_like($item, $_POST['search']['value']);
                }

                if(count($this->column) - 1 == $i) //last loop
                    $this->db->group_end(); //close bracket
            }
            $column[$i] = $item; // set column array variable to order processing
            $i++;
        }

        if(isset($_POST['order'])) // here order processing
        {
            $this->db->order_by($column[$_POST['order']['0']['column']], $_POST['order']['0']['dir']);
        }
        else if(isset($this->order))
        {
            $order = $this->order;
            $this->db->order_by(key($order), $order[key($order)]);
        }
    }

    function get_datatables()
    {
        $this->_get_datatables_query();
        if($_POST['length'] != -1)
        $this->db->limit($_POST['length'], $_POST['start']);

        $this->db->join('kategori', 'kategori.id_kat = produk.kat','left');
        $this->db->join('subkat', 'subkat.id_subkat  = produk.subkat','left');
        $this->db->join('supersubkat', 'supersubkat.id_supersubkat  = produk.supersubkat','left');

        $query = $this->db->get();

        return $query->result();
    }

    function count_filtered()
    {
        $this->_get_datatables_query();
        $query = $this->db->get();
        return $query->num_rows();
    }

    public function count_all()
    {
        $this->db->from($this->table);
        return $this->db->count_all_results();
    }

    public function get_by_id($id_produk)
    {
        $this->db->from($this->table);
        $this->db->where('id_produk',$id_produk);
        $query = $this->db->get();

        return $query->row();
    }

---------------------------------------------
views: v_lihat.php
---------------------------------------------
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Daftar Produk | Admin Panel</title>
    <meta content='width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no' name='viewport'>
    <!-- Bootstrap 3.3.4 -->
    <link href="<?php echo base_url() ?>assets/bootstrap/css/bootstrap.min.css" rel="stylesheet" type="text/css" />
    <!-- FontAwesome 4.3.0 -->
    <link href="<?php echo base_url() ?>assets/font-awesome-4.3.0/css/font-awesome.min.css" rel="stylesheet" type="text/css" />
    <!-- Theme style -->
    <link href="<?php echo base_url() ?>assets/dist/css/AdminLTE.min.css" rel="stylesheet" type="text/css" />
    <link href="<?php echo base_url() ?>assets/dist/css/skins/skin-blue.min.css" rel="stylesheet" type="text/css" />
    <!-- DATA TABLES -->
    <link href="<?php echo base_url() ?>assets/plugins/datatables/dataTables.bootstrap.css" rel="stylesheet" type="text/css" />
    <link href="<?php echo base_url() ?>img/fav.ico" rel="shortcut icon"/>
  </head>
  <body class="skin-blue sidebar-mini">
    <div class="wrapper">

      <?php $this->load->view('Admin/header'); ?>

      <div class="content-wrapper">
        <section class="content-header">
          <h1>Daftar Produk <small>| <?php echo anchor('Admin/produk/tambah/','Tambah Produk') ?></small></h1>
          <ol class="breadcrumb">
            <li><a href="#"><i class="fa fa-dashboard"></i> Produk</a></li>
            <li class="active">Daftar Produk</li>
          </ol>
        </section>

        <section class="content">
          <div class="box">
            <div class="box-body table-responsive padding">
              <button class="btn btn-success" onclick="add_person()"><i class="glyphicon glyphicon-plus"></i> Add Person</button>
              <button class="btn btn-default" onclick="reload_table()"><i class="glyphicon glyphicon-refresh"></i> Reload</button>
              <table id="table" class="table table-striped table-bordered" cellspacing="0" width="100%">
                <thead>
                  <tr>
                    <th>Nama Produk</th>
                    <th>Kategori</th>
                    <th>Sub Kategori</th>
                    <th>Supersub Kategori</th>
                    <th style="width:125px;">Action</th>
                  </tr>
                </thead>
                <tbody></tbody>
                <tfoot>
                  <tr>
                    <th>Nama Produk</th>
                    <th>Harga</th>
                    <th>Warna</th>
                    <th>Action</th>
                  </tr>
                </tfoot>
            </table>
            </div>
          </div>
        </section>

      </div>

      <?php $this->load->view('Admin/footer'); ?>

    </div>

    <!-- jQuery 2.1.4 -->
    <script src="<?php echo base_url() ?>assets/plugins/jQuery/jQuery-2.1.4.min.js"></script>
    <!-- jQuery UI 1.11.2 -->
    <script src="<?php echo base_url() ?>assets/plugins/jQueryUI/jquery-ui-1.10.3.min.js" type="text/javascript"></script>
    <!-- Resolve conflict in jQuery UI tooltip with Bootstrap tooltip -->
    <script>$.widget.bridge('uibutton', $.ui.button);</script>
    <!-- Bootstrap 3.3.2 JS -->
    <script src="<?php echo base_url() ?>assets/bootstrap/js/bootstrap.min.js" type="text/javascript"></script>
    <!-- Slimscroll -->
    <script src="<?php echo base_url() ?>assets/plugins/slimScroll/jquery.slimscroll.min.js" type="text/javascript"></script>
    <!-- FastClick -->
    <script src="<?php echo base_url() ?>assets/plugins/fastclick/fastclick.min.js"></script>
    <!-- AdminLTE App -->
    <script src="<?php echo base_url() ?>assets/dist/js/app.min.js" type="text/javascript"></script>
    <!-- DATA TABLES SCRIPT -->
    <script src="<?php echo base_url() ?>assets/plugins/datatables/jquery.dataTables.min.js" type="text/javascript"></script>
    <script src="<?php echo base_url() ?>assets/plugins/datatables/dataTables.bootstrap.min.js" type="text/javascript"></script>

    <script type="text/javascript">
    var save_method; //for save method string
    var table;

    $(document).ready(function() {

        //datatables
        table = $('#table').DataTable({

            "processing": true, //Feature control the processing indicator.
            "serverSide": true, //Feature control DataTables' server-side processing mode.
            "order": [], //Initial no order.

            // Load data for the table's content from an Ajax source
            "ajax": {
                "url": "<?php echo site_url('Admin/produk/ajax_list')?>",
                "type": "POST"
            },

            //Set column definition initialisation properties.
            "columnDefs": [
            {
                "targets": [ -1 ], //last column
                "orderable": false, //set not orderable
            },
            ],

        });

        //datepicker
        $('.datepicker').datepicker({
            autoclose: true,
            format: "yyyy-mm-dd",
            todayHighlight: true,
            orientation: "top auto",
            todayBtn: true,
            todayHighlight: true,
        });

        //set input/textarea/select event when change value, remove class error and remove text help block
        $("input").change(function(){
            $(this).parent().parent().removeClass('has-error');
            $(this).next().empty();
        });
        $("textarea").change(function(){
            $(this).parent().parent().removeClass('has-error');
            $(this).next().empty();
        });
        $("select").change(function(){
            $(this).parent().parent().removeClass('has-error');
            $(this).next().empty();
        });

    });
    </script>