1) construct function commented as protected, not declared as such.
2) several methods declared with underscore preceding name, but each
one is neither declared as private nor commented as such
3) Property $_key is commented as private but not declared as such.
This affects the way I test the file, so I'm going to assume the
underscored methods and property are private and the construct is not
protected (because if it *is*, then I'm going to have to devise a
completely different way to test it). Let me know if that's wrong.