This is a continuation of the basic installation, please read that first!
A slightly more flexible way to setup Smarty is to extend the class and initialize your Smarty environment. So instead of repeatedly setting directory paths, assigning the same vars, etc., we can do that in one place.
Lets create a new directory /php/includes/guestbook/ and make a new file called setup.php. In our example environment, /php/includes is in our include_path. Be sure you set this up too, or use absolute file paths.
Now lets alter the index.php file to use setup.php:
Now you see it is quite simple to bring up an instance of Smarty, just use Smarty_GuestBook() which automatically initializes everything for our application.