public function editBiaya($id = null, $tab = null)
 {
     if (Session::get('role') != 2) {
         $this->display();
         exit;
     }
     if ($id != "") {
         $biaya = new Biaya();
         $data_biaya = $biaya->get_by_id($id);
         //mendapatkan data biaya berdasarkan id=kd_biaya
         //var_dump($data_biaya);
         $kontrak = new Kontrak();
         //$kd_kontrak = $_POST['kd_kontrak'];
         $data_kontrak = $kontrak->get_by_id($data_biaya->kd_kontrak);
         //var_dump($kontrak);
         $universitas = new Universitas($this->registry);
         $univ = $universitas->get_univ_by_jur($data_kontrak->kd_jurusan);
         $nama_univ = $univ->get_kode();
         //mendapatkan nama singkatan universitas
         $kontrak_lama = $kontrak->get_by_id($data_kontrak->kontrak_lama);
         //mendapatkan objek kontrak lama
         //var_dump($kontrak_lama);
         //echo $kontrak_lama->no_kontrak;
         if ($kontrak_lama != false) {
             $kon_lama = $kontrak_lama->no_kontrak;
         } else {
             $kon_lama = "";
         }
         $jurusan = new Jurusan($this->registry);
         $jurusan->set_kode_jur($data_kontrak->kd_jurusan);
         $jur = $jurusan->get_jur_by_id($jurusan);
         //var_dump($jur->get_nama());
         $nama_jur = $jur->get_nama();
         //mendapatkan nama jurusan
         //menampilkan daftar biaya berdasarkan kontrak
         if ($tab == "" || $tab > 2) {
             $tab = 0;
         }
         $this->view->total_biaya_kontrak = $biaya->get_biaya_by_kontrak($data_biaya->kd_kontrak);
         $this->view->nama_univ = $nama_univ;
         $this->view->nama_jur = $nama_jur;
         $this->view->biaya = $data_biaya;
         $this->view->kontrak = $data_kontrak;
         $this->view->tab = $tab;
         $this->view->render('kontrak/edit_biaya');
     } else {
         header('location:' . URL . 'kontrak/display');
     }
 }