Checking for notifications on rest of website
I have a website that has a vanilla forum embedded inside of it (all on the same host). The rest of the website uses PHP and MySQL; however, I would like to add something at the top of each page that would let users know if they have a notification in their forum account (e.g. if someone receives a new private message, there would be a notification at the top right of each page on the website). How might I be able to do this?