vojtechsanda/ajax-chat-app ? reverse-engineered prompt

Build me a simple web chat app that works with a PHP API and plain JavaScript, using AJAX so messages update without reloading the page.

I want a clean basic chat experience where people can type messages, send them, and see new messages appear smoothly. Include the backend API endpoints and the frontend pages needed to make it work, plus a simple layout in the browser. Keep it lightweight and straightforward, since this is meant to be a small vanilla JS project, not a big framework app.

If you need to, look up current docs online for anything unclear, but keep the final result simple and easy to run locally. It would be great if the app also has a basic place for user profile settings and some simple protection against spam, even if it is just a first version.