Responsive design via PHP?

Question

PHP

Is it possible to make a mobile version of the site through PHP, i.e. we read the user's screen size and use PHP to substitute the required css file in the page header, or do we need to do it through media queries?

Answer 1

PHP can't determine the user's screen size, it's a server-side language.
Such actions are resolved, as you yourself wrote, through media queries.

Answer 2

Through the media. besides, as I understand it, even if through php it would be possible, but when resizing the window, it would not adapt.