How can I use a database in another server?

[Rocking80]

I only changed connectDB.php file with the database IP and credential, seems not work.
the register.php can be displayed in the page, but when I finished the form and submit the page show error. I tried to change the servername in register.php file, and also the new user cannot be inserted in the database.

          $servername = "192.168.0.47";
          $username = "root";
          $password = "xxxxxxxx";

Could you please update all the page code to use outer database?