How to understand the structure of classes (objects) in CMS?

Question

PHP

For example, there is OpenCart, it is clearly assembled according to MVC, you can see where the router is and so on, but how to figure out which class does what, what other classes it refers to, and so on? Are there any schemes or manuals of this kind, or is there only one way out - to read the code?
How do you understand other people's code? (on OOP)

Answer 1

debugging

Answer 2

It is important to set the target correctly.
You don't need to know exactly how OpenCart is written.
You just need to figure out how to work with it.
And for this, the code that many people use has manuals, articles, samples, and ready-made hautushki.

Answer 3

Open the project in phpstorm.
In some cases, it will be possible to build a class connection diagram.
Install xdebug extension for php.
Set up debugging in phpstorm.
For example, click on the button "Add to cart"
And away we go...

Answer 4

RTFM?
docs.opencart.com/en-gb/developer/module