how to fix this problem

mugi

DataTables warning: table id=table - Invalid JSON response. For more information about this error, please see http://datatables.net/tn/1

var save_method; //for save method string
var table;

$(document).ready(function() {

//datatables
$('#table').DataTable({ 
    "bPaginate": true,
      "bLengthChange": false,
      "bFilter": true,
      "bSort": true,
      "bInfo": true,
      "bAutoWidth": false,
    "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('person/ajax_list');?>",
        "type": "POST"
    },

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

});

tangerine

Did you carry out the diagnostics process explained at http://datatables.net/tn/1 ?