How to support multiple API versions?

Question

PHP

Hello! I have a website and an API for the application.
The site is written in PHP with the MVC pattern, so the API uses part of the functionality (model) for its own needs.
those. for example, the authorization model is great for both the site and the application API / As a result, it turned out that, in fact, the site has its own controller, and API version 1 is a different controller.
All API files are in a separate folder.
The problem is this... If another version of the API is needed, it turns out that I need to make a duplicate of the API directory on the server and, roughly speaking, add the number 2 to it and redo it?
But here Another question, it turns out, when changing site models, you need to constantly monitor that these changes do not affect any of, say, a dozen API versions? Somehow it doesn’t converge (( Tell me with advice where I didn’t turn there ....