Dont know if this is possible.
I need to create a new mysql user with access to only databases with database name with prefix say user_db_.
I have a php application in which when a new user is added it creates a database user_db_'userid'. Suppose three users are created such that their databases are user_db_1, user_db_2, user_db_3.
I need to create a new user say user_accounts which has access to only user_db_1, user_db_2, user_db_3,..........,user_db_n.