How to deal with ecshop source code

I want to learn the source code of ecshop during this period. Where can I start from? I was a little dizzy at first, but I didn't see any effect after reading it for a long time, I think you should first make up the basics and better APS for conversion. The first thing you need to do is to make up the content functions of oop, because some of the methods are slightly different from those of asp, and I will learn the ecshop source code method later.
I want to learn the source code of ecshop during this time. Where can I start from? I was a little dizzy at first, but I didn't see any effect after reading it for a long time.

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I think it is better to complete the basics first.
The first thing we need to do when converting APS is the content of oop.
Functions also need to be supplemented, because some of them are slightly different from asp.
It will be much easier to go back to the page after the foundation is fully enriched.
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For ECSHOP, it is recommended that you first read the shopping cart, pay by bank, and then look at the table structure.