On his blog today Vance Lucas has posted a method you can use to only get the properties of your class that are in the "public" scope.

PHP provides two built-in functions to retrieve properties of a given class – get_object_vars and get_class_vars. Both these functions behave the same exact way, one taking an object as a variable and the other taking a string class name. The tricky thing about the two functions is that they behave differently depending on the call scope, returning all of the class variables available within the called scope.

As a bit of a hack (in lower than PHP 5.3) he shows how to use the create_function function to create a small statement in a different scope that returns the only the variables seen from the "outside" - just the public ones. PHP 5.3 users can do it much more cleanly with closures. Code examples for both are included.