Need Help in advancing my knowledge base

If you want to know how to write test code,
our book "CodeIgniter Testing Guide"
https://leanpub.com/codeigniter-testing-guide might help you.

To be honest, the book is a bit out of dated, but if you know CodeIgniter3,
you can probably read it easily.

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If you don't read this, I recommend to read:

PHP: The Right Way
https://phptherightway.com/

Thanks @kenjis I will look into those resources.