(PHP) How to detect that user's computer/browser is in Dark Mode?

Question

Lately I am updating my software to support dark mode, in response to research that looking at a paper-white background display is bad for the eyes and for sleep rhythms. Is

Answer 1

Since PHP executes on the server without any knowledge of the client, there is no direct way of finding this out.

If it is possible to detect the color mode in JS, you could embed a small JS script to your site, that sets a cookie. Cookies are transmitted to the server on request, so PHP is able to query them.