Registry means registering or creating a new variable which is to be used later on in the project/code. The registry variable acts as a global variable which can be used anywhere.
We register a variable with register() function.
We can unregister the variable with unregister() function.
To fetch the registry variable, we use registry() function.
We can store anything in the registry variable. It can be integer, string, array, etc.

Before I had posted an article to add, edit, delete, and display contents. I had also included sessions there. There was the facility to login and register users too.
But i got feedback that it was a bit complex for novice users of PHP (users who have just started PHPing). It was a kind of full-fledge system with PHP, MySQL and session.

Hello everyone! here is a simple and complete tutorial to add, edit, delete, login, and register in PHP with MySQL database.
The description is present in the code.. in comments :D I hope those comments are sufficient to describe the code. The database part is in the sql file named ‘database.sql’.