PHP CRUD allows you to create, read, update, and delete
records from your database. With CRUD you can create pages to list and edit your
MySQLi is an extension used in PHP to communicate with databases. It offers many benefits (over MySQL) including being more secure and taking advantage of an object oriented interface. This is a great and practical way to learn database communication and object oriented programming techniques with PHP.
Combining both CRUD and MySQLi will move you on your way to becoming a good and practical PHP programmer.