Determination of the user's language and subsequent redirection - how?

Question

PHP

The site needs to implement a page with PHP and/or JavaScript code, which, when visited, automatically determines the user's language (Russian or English), and then redirects to the appropriate section. That is: site.com/index.php -> site.com/ru/index.php or site.com/index.php -> site.com/en/index.php.

Answer 1

$_SERVER['HTTP_ACCEPT_LANGUAGE']