Create a php install script to install on MySql

I need an install script done up so that one of my staff can do installs to different domains. i need you to have good sql, php and cpanel knowledge so that it will install with the different cpanel skins. It needs to check that the database exists and set up the usernames for that database without us having to do it manually. I already have an install script that doesn't work but will give you an idea of how it works. Part of the install includes writing the usernames and passwords to a file to be used as a config file when the user logs in next time.