PHP 5 Power Programming

3.15. final Methods

Until now, you have seen that when you extend a class (or inherit from a class), you may override inherited methods with a new implementation. However, there are times where you might want to make sure that a method cannot be re-implemented in its derived classes. For this purpose, PHP supports the Java-like final access modifier for methods that declares the method as the final version, which can't be overridden.

The following example is not a valid PHP script because it is trying to override a final method:

class MyBaseClass { final function idGenerator() { return $this->id++; } protected $id = 0; } class MyConcreteClass extends MyBaseClass { function idGenerator() { return $this->id += 2; } }

This script won't work because by defining idGenerator() as final in MyBaseClass, it disallows the deriving classes to override it and change the behavior of the id generation logic.