A reliable way to find unused files and code?

Question

PHP

Classes, methods, files, css and so on and so forth.
It is also worth considering that there are, for example, files that are used by the API.
It comes to mind to intercept the request and write down the unique files that are used.

What packages, plugins, analyzers, techniques?

Answer 1

SonarQube and let's go. Perform a full code analysis