public function delBiaya($id = null)
 {
     if (Session::get('role') != 2) {
         $this->display();
         exit;
     }
     if ($id != "") {
         $biaya = new Biaya();
         $data = $biaya->get_by_id($id);
         $biaya->deleteBiaya($id);
         ClassLog::write_log("kontrak", "hapus biaya kontrak", "kode biaya " . $id . "kode kontrak" . $data->kd_kontrak);
         //echo $data->kd_kontrak;
     }
     header("Location:" . URL . "kontrak/biaya/" . $data->kd_kontrak);
 }