MySQL Username and Pass w/PHP

Hey, I wanted to know how I can create a new user for MySQL through PHP using variables from a form.

I am creating a script that installs another script that I'm planning to write. The user inserts a database name, database password, and username, and I want the script to create all three of those things. (In short, its using the variables to define what the username and password for the database they create will be.

If anyone can help, that would be great.
(If it helps, teh variables for the three are:
1) $databasename (for the database name)
2) $username (for the username)
3) $password (for the password))

Thanks,
Frank