This pattern provides an easy way to decouple many components working together. It is a good alternative to Observer IF you have a "central intelligence", like a controller (but not in the sense of the MVC).
All components (called Colleague) are only coupled to the Mediator interface and it is a good thing because in OOP, one good friend is better than many. This is the key-feature of this pattern.
You can also find this code on GitHub
Mediator.php
Mediator.php
Colleague.php
Colleague.php
Ui.php
Ui.php
UserRepository.php
UserRepository.php
UserRepositoryUiMediator.php
UserRepositoryUiMediator.php
Tests/MediatorTest.php
Tests/MediatorTest.php