Creating a Custom WordPress Messaging System – Envato Tuts+ Code Tutorials
It’s possible to implement a system that allows us to programmatically set our own custom messages, their type, and when and where to display them on the administration page. And that’s what this series is going to cover.
Source: https://managewp.org/articles/14114/creating-a-custom-wordpress-messaging-system-envato-tuts-code-tutorials
source https://williechiu40.wordpress.com/2017/01/03/creating-a-custom-wordpress-messaging-system-envato-tuts-code-tutorials/