What is the best way to organize plug-ins for a WEB-portal?

Question

PHP

Hello!
I would like to know the best practices for developing plug-ins for WEB applications.
Now we have an implemented data model, and the possibilities for filling it (PHP + bootstrap + postgresql)
We need to carry out calculations of a different nature on these data. In the future, calculation methods and requirements for displaying results may change in different ways. We decided to develop a mechanism and add modules (plugins) to the model.
Can you tell me how best to organize the project structure / source code?
It is understood that a module can have its own representation.
ps "hot" connection / disconnection of modules is not required
Thank you! :)