jQuery Datatables服务器端处理无结果返回

Question

按照标题所述，我有以下代码使用datatables服务器端处理来获取表中的数据，但最终没有返回结果：

    include(mysqli_db.php);

    $request = $_REQUEST;

    $col = array( 
        0  => 'id', 
        1  => 'name', 
        2  => 'phone',
        3  => 'ic_pp_no',
        4  => 'passport_no', 
        5  => 'email',
        6  => 'address1',
        7  => 'address2', 
        8  => 'country',
        9  => 'pp_expiry_date',
        10 => 'created_date'
    );

    $q   = "SELECT * FROM account";
    $sql = $mysqli->query($q);
    $totalData = $sql->num_rows;
    $totalFilter = $totalData;

    $data = array();
    while($row = $sql->fetch_object()){
        $subdata = array();
        $subdata[] = $row->name;
        $subdata[] = $row->phone;
        $subdata[] = $row->ic_pp_no.$row->passport_no;
        $subdata[] = $row->email;
        $subdata[] = $row->address1.$row->address2;
        $subdata[] = $row->country;
        $subdata[] = $row->id;
        $data[] = $subdata;

    }

    $json_data = array(
        'draw'            => intval($request['draw']),   
        'recordsTotal'    => intval($totalData),  
        'recordsFiltered' => intval($totalFilter),
        'data'            => $data
    );

    echo json_encode($json_data);

我可以看到json输出的行数准确，但没有数据：

  

{“绘制”：0，“ recordsTotal”：81，“ recordsFiltered”：81，“数据”：[]}

谢谢。