php - How to implement a plug-in similar to WordPress?

Question

I have never figured out how to implement plug-ins. After all, some functions involve databases, etc.
Installation and uninstallation of plug-ins, especially since I have mysophobia, will there be any residue after uninstalling?
Can you give me some ideas or examples?

Answer 1

I recommend you two articles

Develop a plug-in (official tutorial)

How to develop a WordPress plugin