Mattias Noback shares how you can migrate a code base that fetches its dependencies using static method calls to code that uses dependency injection.

I've worked with several code bases that were littered with calls to Zend_Registry::get(), sfContext::getInstance(), etc. to fetch a dependency when needed. I'm a little afraid to mention façades here, but they also belong in this list. The point of this article is not to bash a certain framework (they are all lovely), but to show how to get rid of these "centralized dependency managers" when you need to.

https://matthiasnoback.nl/2018/06/road-to-dependency-injection/