You only need one database, just make sure that you have a user_id in each of your tables then you will have the same end result as a database per user.
The only reason that I can see to keep them in seperate databases is if you have absurdly large data in the tables and lots of traffic but then maybe you shouldn't use a single app but rather one for each user/set of users.
my boss let me do this i'm not clearly purpose of him but i think it should be can just change database connection when user login if anyone know help please i trying so long time