Help to apply onion architecture in codeIgniter

I want to apply the Onion Architecture or the AKA Uncle bob architecture because in the book that I have some examples that gives toy the opportunity to separate the business logic from the view and framework and also you are independence from databases. You can change php framework very easy. You can see a clean architecture project
https://github.com/romainkuzniak/symfony...chitecture
https://phutai.me/wp-content/uploads/201...Wilson.pdf
Go to the page 69.