horizontal menu i assume means a toolbar type of thing
and pgSql is mysql yes?
whatever...
once the user logs in u pull out of a table the functions they are allowed to use in the app ... how u store this user info depends on what kind of user security system u have implemented
in an app i wrote a whiles ago (c++/windows/financial markets) there was a permissions table that identified what actions each user could do
generating the actual toolbar / menu is trivial when u have the permissions thing sorted out