I finally found out what had been missing in your model.
Firstly, add the following lines to pass variables in save.php
Secondly, add a program, which I called schemagen.php.
// Builds the DataObjects classes
$_SERVER['argv'] = 'example.ini';
I have seen this article translated and posted in simplified Chinese in several sites. Anyway, your model will become the backbone of my first commercial project.