php - DatabasePHP: Created user A accesses Database of created user B and vice versa

Solution:

What you're describing isn't really how databases work. I won't go into exactly how to do this, because there are many good resources online, but it's best to think of a database as a central store of information that everyone accesses. Instead of having each person have their own database, we generally associate each person with an identifier, either an ID or username. We then associate stored information with this identifier. For example, we might have a timesheets table with the columns:

id,punch_in,punch_out,employee_id

Then, when getting the time records for a given employee, you would do something like:

SELECT punch_in,punch_out FROM timesheets WHERE employee_id = MY_EMPLOYEE_ID

The above statement says: "Get all punches in and punches out from the timsheets table, as long as they match a certain employee ID." You can go much deeper than this, but this is an effective way to segment data records and keep everyone's data to themselves. If all you have is a user name, you can use something called a join, which merges two tables on a shared index.

There are many ways to achieve these goals, but the key takeaway of setting up a database is that each distinct type of thing should have its own table, for example a table for employees and one for timesheets, and if they relate to each other, they should share an index so you can associate them with each other.

You'll find lots of good resources here.

Solution:

Although it is possible to set permissions at a more granular level, in MySQL and most DBMS it is simplest to do at the database level. Note that a single instance of MySQL can (and likely already does) have multiple databases. So your first task is to seperate the functionality out into different databases, then apply appropriate permissions for each user, making sure you don't alreay have permissions set against a wildcard username.