A PHP-powered online TODO-List with json files for storage

Live version without PHP: login.html

I wanted a simple, fast-loading non-bloated todo list that I can access from every device that has internet. I made it with PHP and JSON-Files for Storage.
PHP is easy to use for such small projects and a database would've been overkill for such small data, which is why i used json files for the storage of todos.

The main flaw this has is the fact that if someone finds the folder of the JSON files, they can simply read everyones todos. This can be circumvented by using access-rights.

Project can be downloaded here.