PHP in Action

Chapter 3. Using PHP classes effectively

3.1	Visibility: private and protected methods and variables	41
3.2	The class without objects: class methods, variables, and constants	49
3.3	Abstract classes and methods (functions)	56
3.4	Class type hints	57
3.5	Interfaces	60
3.6	Summary	64

From stone axes to passenger airlines, objects—real, tangible ones—are ubiquitous in technology. From that perspective, it’s hardly surprising that software technology has come to depend on virtual objects. Classes, on the other hand, are something else. Naming, putting things into categories or classes, is inherent in natural language, but talking about categories of things and the process of naming is foreign to physical technology. Classes come out of philosophy ...