Though you would expect settings.php to be available to view.php because it was included in a script that includes them both, I have found that this usually isn't the case. You have a couple of choices:
- require_once all the files each class needs in each class file
- write an __autoload() function so that PHP can find all your classes whenever it thinks it needs one
The 2nd option is more flexible.
If you want to know classes are available from a particular place try outputting get_declared_classes()
