It really depends on what type of application it is.
You could have and application that has separate backend and frontend.
In CodeIgniter 4 we now have modules so we can divide our applications
into modules.
Example
Admin Module
Blog Module
CMS Module
etc;
CodeIgniter 4 is just about ready to be released soon so I would start by
designing my new application using CodeIgniter 4 and modules.
That is what I' am doing using now. Building my admin dashboard using
AdminLTE.
The nice thing about using modules is that once made they are reusable.
What did you Try? What did you Get? What did you Expect?
Joined CodeIgniter Community 2009. ( Skype: insitfx )