How to dynamically show new notifications using?

thanks for giving your time .

I have a webpage which fetch "Notifications " created by admin to users from a MYSQL database using PHP script. Now i want to that if Admin create a new notification It should be Dynamically added to user page.

just like Facebook , when a user is logged in and his friend post something , at that instant i can see a Notification of new post Without reloading the page.