Datatables, wrong results after pagination

When i have sorted my table, i'm getting some records double in the second page and some other records are not shown.

it's the first time i'm using datatables, it's a table to get records back of all shops created on the website. While i'm going to the next page, sometimes one of my records is gone and instead there is a double record from the first page.

public function winkeltables()
 {
     $table = 'alle_winkels';
     $primaryKey = 'w_id';
     $id = $_GET['k_id'];
     $columns = [
         ['db' => 'w_logo', 'dt' => 0, 'formatter' => function ($d, $row) {
             if ($d == "") {
                 return "";
             }
             return "<img class='thumb' src='/" . $d . "'/>";
         }],
         ['db' => 'k_beoordeling', 'dt' => 1, 'formatter'=> function($d, $row){
             return beoordeling($d);
         }],
         ['db' => 'w_naam', 'dt' => 2],
         ['db' => 'w_land', 'dt' => 3],
         ['db' => 'w_straat', 'dt' => 4],
         ['db' => 'w_postcode', 'dt' => 5],
         ['db' => 'w_woonplaats', 'dt' => 6],
         ['db' => 'w_id', 'dt' => 7, 'formatter' => function ($d, $row) {
             return "<a data-id='" . $d . "' href='/winkeldetail?w_id=" . $d . "'>Bekijk</a>";
         }],
     ];
     $sql_details = [
         'user' => 'x',
         'pass' => 'x',
         'db' => 'x',
         'host' => 'x'
     ];

     if($id != "")
     {
         $where = ["k_id = " . $id];
         echo json_encode(
             \SSP::complex($_GET, $sql_details, $table, $primaryKey, $columns, $where)
         );
     }
     else{
         echo json_encode(
             \SSP::simple($_GET, $sql_details, $table, $primaryKey, $columns)
         );
     }

     die;
 }

The script in my view is:

<script>
    $(document).ready(function() {
        var dt = $('#example').DataTable({
            "processing": true,
            "serverSide": true,
            "ajax": "/datatables/winkel",
            "language": {
                "url": "http://cdn.datatables.net/plug-ins/9dcbecd42ad/i18n/Dutch.json"
            }
        });
        $('#example tbody').on( 'click', 'tr', function () {
            var url = $(this).find('td').last().find('a').attr('href');
            if(url) {
                window.location = url;
            }
        } );
    });
</script>

I am using the standard files from www.datatables.net

I already solved my own problem. I solved my problem by adding another order in my ssp.php file.

The new code is:

if ( $requestColumn['orderable'] == 'true' ) {
                $dir = $request['order'][$i]['dir'] === 'asc' ?
                    'ASC' :
                    'DESC';

                $orderBy[] = '`'.$column['db'].'` '.$dir . ', '. '`'.'w_naam'.'`'. ' ASC';
            }

The old code was:

if ( $requestColumn['orderable'] == 'true' ) {
                $dir = $request['order'][$i]['dir'] === 'asc' ?
                    'ASC' :
                    'DESC';

                $orderBy[] = '`'.$column['db'].'` '.$dir;
            }

I dont know if this code is efficient, but atleast it works now!