Object-Oriented PHP

Abstract Classes

In Chapter 10 we saw that if a derived class does not implement all the methods of an interface, then it must be declared abstract. Let's push this concept to the extreme and see what a completely abstract class might look like. Listing 11-1 shows the definition of such a class.

Listing 11-1. The definition of the abstract class Bird

❶abstract class Bird{ protected $plumage; protected $migratory; abstract public function __construct(); abstract public function fly(); abstract public function sing(); abstract public function eat(); abstract public function setPlumage($plumage); abstract public function getPlumage(); abstract public function setMigratory($migratory); abstract public function getMigratory(); }

As we saw in ...