Interface (C++ and PHP Cross Reference Guide)

An element of coding where you define a common set of properties and methods for use with the design of two or more classes.

Both interfaces and abstract classes are types of abstraction. With interfaces, like abstract classes, you cannot provide any implementation. However, unlike abstract classes, interfaces are not based on inheritance. You can apply an Interface to any class in your class tree. In a real sense, interfaces are a technique for designing horizontally in a class hierarchy (as opposed to inheritance where you design vertically). Using interfaces in your class design allows your system to evolve without breaking existing code.

C++:  "Interfaces" No, but mimic it. You can mimic an interface by using a class that has only pure-virtual functions and no member variables.  C++ Interfaces (No, but mimic it.)

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