even default values. You can set up classes that allow you to create an object and set all
its properties in one statement. Unlike other languages, PHP does not allow for
destructors—functions that execute when the instance is deleted. However, if you choose
to use unset on an object, all the memory associated with that object will be freed. In
situations where you must execute some code when you finish using an object, create
your own shutdown function and remember to call it.
One powerful aspect of classes is inheritance, the idea that a class can extend the
functionality of another class. The new class will contain all the methods and properties
of the class it extends, plus any others it lists within its body. You may also override
methods and properties from the extended class. As shown in Figure 6–1, you extend a
class using the extends keyword.
Listing 6.1 Using Classes