Error: Unable to open the database file

[Mike Bonner]

Actually, you CAN connect directly to to mysql server (its actually a
server in its own right) if you set things up that way.  You have to change
where connections are allowed from but honestly, you're still better off
using middleware. This way you can place any files with sensitive data
(passwords etc) outside the directly accessible area of your webserver, and
have your middleware "include" the file. In this way, you make it harder
for people to poke around and figure out parts of your setup, and obviates
the need to have a hard coded or known password to your mysql database.

Having an open port accessible from anywhere directly to your database
server is usually a bad idea.
The php middleware idea should work swimmingly.