Codeigniter：当用户登录以显示通知时，仅调用一次控制器

Question

I have created a notification library to generate different types of notifications for different user groups. What I want is that when a user logged in my Notifications.php should be invoked to generate all the notifications for that user. In Notifications.php controller I will fetch the data from the database and based on some conditions I will generate a notification. I was thinking of using hooks in CI to do that but the problem is that Notifications.php will be invoked every time user move from one page to another page in the application. How can I prevent Notifications.php to be invoked multiple times?