Do nodejs have any suggestions for the chat system?

  node.js, question

The internship is doing a project, written by Yii2, and the database is mysql.
The project requires a chat system
I plan to use socket.io and express as a small communication system between users and customer service.
The function is communication between users and customers.
Chatroom one-on-one preservation of historical records, do not want to use mongodb, mysql can be shared here?
I have just contacted node. Do you have any good reference to demo or ideas?
Can php and node coexist?
= = I don’t quite understand

The main problem is the authority problem. node inside does not know what to do.

My graduation design, simple chat system, socket.io plus Express plus MySql, code is a little Low
https://github.com/vu-ji/h5Chat