THIS IS CONSIDERED TO BE AN ANTI-PATTERN!
Service Locator is considered for some people an anti-pattern. It violates the Dependency Inversion principle. Service Locator hides class' dependencies instead of exposing them as you would do using the Dependency Injection. In case of changes of those dependencies you risk to break the functionality of classes which are using them, making your system difficult to maintain.
To implement a loosely coupled architecture in order to get better testable, maintainable and extendable code. DI pattern and Service Locator pattern are an implementation of the Inverse of Control pattern.
With ServiceLocator you can register a service for a given interface. By using the interface you can retrieve the service and use it in the classes of the application without knowing its implementation. You can configure and inject the Service Locator object on bootstrap.
You can also find this code on GitHub
Service.php
Service.php
ServiceLocator.php
ServiceLocator.php
LogService.php
LogService.php
Tests/ServiceLocatorTest.php
Tests/ServiceLocatorTest.php