code: private function setParam($key, $value, $allowed_keys)
      {
          if (in_array($key, $allowed_keys)) {
              $this->{$key} = $value;
          }
      }
docs: Set valid Access Point.
  
  @param  string  $key
  @param  mixed  $value
  @param  array  $allowed_keys
  @return void