/**
  * Display class in which user attend. 
  * @param  [String] $id [description]
  * @return [type]     [description]
  */
 function getClass($user_id)
 {
     $result = array();
     if (isset($user_id)) {
         $model = new User_Class_Model();
         $class_id = $model->selectWhere(array('class_id'), "user_id = " . "'{$user_id}'");
         if (isset($class_id)) {
             $class_model = new Class_Room_Model();
             foreach ($class_id as $key => $value) {
                 $record = $class_model->selectWhere('*', "id = " . $value['class_id']);
                 array_push($result, $record[0]);
             }
         }
         if (isset($result)) {
             echo json_encode($result);
         }
     }
 }
 /**
  * User join in class
  * @return [type] [description]
  */
 function join()
 {
     if (!isset($_POST['submit'])) {
         echo json_encode("failed");
         exit;
     }
     $data = array();
     $data['class_id'] = $_POST['class_id'];
     $data['user_id'] = $_POST['user_id'];
     if (count($data) == 0) {
         echo json_encode("failed");
         exit;
     }
     $UserClassModel = new User_Class_Model();
     $UserModel = new User_Model();
     $class_id = $data['class_id'];
     $user_id = $data['user_id'];
     $isAttend = ${$UserClassModel}->selectWhere('*', "class_id = '{$class_id}' and user_id = '{$user_id}'");
     $isExistClass = $this->selectWhere('*', "id = '{$class_id}'");
     $isExistUser = $UserModel->selectWhere('*', "id = '{$user_id}'");
     if (isset($isAttend)) {
         echo json_encode(array("failed", 'message' => 'You are attend this class!'));
         exit;
     }
     if (!isset($isExistClass) || !isset($isExistUser)) {
         echo json_encode(array("failed", 'message' => 'Class or user not exist!'));
         exit;
     }
     $arrTemp = array();
     foreach ($data as $key => $value) {
         $arrTemp[$key] = $key . "=" . "'{$value}'";
     }
     if ($UserClassModel->insert($data)) {
         echo json_encode(array("success", $data['id']));
     } else {
         echo json_encode("failed");
     }
 }