This was my A-level OCR Computer Science project. It is a to-do style list application using raw PHP and SQL backend and raw JS with a bit of Jquery for the AJAX calls for the frontend.
There is an account system with password hashing. Then users can then create a checklist which would save in real-time using AJAX calls. The checklist would get a custom link on the website similar to how pastebin works. Users could also set a password on their checklist if they did not have an account. You could also set the visibility of your checklists: visible and editable, just visable, not visible with the password. Users have the same options but they don't need a password as they are signed into the account.