public function isLoggedIn() {
    if(count($this->userInfo)) {
      $id = !empty($this->userInfo['id']) ? intval($this->userInfo['id']) : false;
      $username = !empty($this->userInfo['username']) ? $this->userInfo['username'] : false;
      $password = !empty($this->userInfo['password']) ? $this->userInfo['password'] : false;
      if($id !== false && $username !== false && $password !== false) {
        try {
          $stmt = $this->prepare("SELECT id, username, password FROM users WHERE id = :id AND username = :username AND password = :password LIMIT 1");
          $stmt->bindParam(":id", $id, PDO::PARAM_INT);
          $stmt->bindParam(":username", $username, PDO::PARAM_STR);
          $stmt->bindParam(":password", $password, PDO::PARAM_STR);
          $stmt->execute();
          $stmt->bindColumn("id", $id, PDO::PARAM_INT);
          $stmt->bindColumn("username", $username, PDO::PARAM_STR);
          $stmt->bindColumn("password", $password, PDO::PARAM_STR);
          $result = $stmt->fetch(PDO::FETCH_BOUND);
          if($result) {
            return $this->userInfo === compact("id", "username", "password");
          }
        } catch(PDOException $e) {
          die("PDO Error: ({$e->getCode()}) {$e->getMessage()}");
        }
      }
    }
    return false;
  }