How to debug large applications?

Question

PHP

Got a fairly large project. Lots of modules and components, all scattered in different places. There is no documentation as such for the project.
Most likely in an MVC application, because there are controllers and some templates, but I can't understand which ones are currently used. Maybe you can somehow use xdebug to see what files the application entered during operation? Please advise how to figure out how it all works.
PS: running xdebug manually through the application is not an option)

Answer 1

php:debug-backtrace