var oTable = $('#big_table').dataTable( {
          "aoColumnDefs": [
  { "sWidth": "20%", "aTargets": [ 6 ] }
],
    "bProcessing": true,
    "aaSorting": [[0,'desc']],
    "bServerSide": true,
    "sAjaxSource": '<?php echo base_url(); ?>agent/order/list_order',
            "bJQueryUI": true,
            "sPaginationType": "full_numbers",
            "iDisplayStart ":25,
            "oLanguage": {
        "sProcessing": "<img src='<?php echo base_url(); ?>img/ajax-loader.gif'>"
    },
    "fnInitComplete": function() {
            //oTable.fnAdjustColumnSizing();
     },
    "fnRowCallback": function( nRow, aData, iDisplayIndex ) {
        nRow.className = aData[5];
    },
    'fnServerData': function(sSource, aoData, fnCallback)
        {
          $.ajax
          ({
            'dataType': 'json',
            'type'    : 'POST',
            'url'     : sSource,
            'data'    : aoData,
            'success' : fnCallback
          });
        }
} )
dataTable.columnFilter({
        sPlaceHolder: "head:before",
        aoColumns: [ null,
                    { type: "select", values: [ '-01-', '-02-', '-03-', '-04-', '-05-', '-06-', '-07-', '-08-', '-09-', '-10-', '-11-', '-12-'] },
                    null,
                    null,
                    null,
                    null,
                    null,
                    ]
    });

<script src="<?php echo site_url('js/datatables/jquery.dataTables.js'); ?>"></script>
    <script src="<?php echo site_url('js/datatables/jquery.dataTables.columnFilter.js'); ?>"></script>