NullOutput is a example of NullObject pattern. It is not formally a Design Pattern by the GoF but it's a schema which appears frequently enough to be a pattern. Furthermore it is a really good pattern in my opinion:
- the code in the client is simple
- it reduces the chance of null pointer exception
- less "if" => less test cases
Every time you have a method which returns an object or null, you should return an object or a NullObject. With NullObject, you don't need
a statement like if (!is_null($obj)) { $obj->callSomething(); } anymore.
- Symfony2: null logger of profiler
- Symfony2: null output in Symfony/Console
- null handler in a Chain of Responsibilities pattern
- null command in a Command pattern