/**
  * Return safe user data.
  * @param user id not required
  * @return user object or false
  */
 public static function user($id = 0)
 {
     if ($id) {
         return User::model()->active()->findbyPk($id);
     } else {
         if (Yii::app()->user->isGuest) {
             return false;
         } else {
             if (!self::$_user) {
                 self::$_user = User::model()->active()->findbyPk(Yii::app()->user->id);
             }
             return self::$_user;
         }
     }
 }