According to the PHP manual, a class like this:

abstract class Example {}

cannot be instantiated. If I need a class without instance, e.g. for a registry pattern:

class Registry {}
// and later:
echo Registry::$someValue;

would it be considered good style to simply declare the class as abstract? If not, what are the advantages of hiding the constructor as protected method compared to an abstract class?

Rationale for asking: As far as I see it, it could a bit of feature abuse, since the manual refers to abstract classes more as like blueprints for later classes with instantiation possibility.