set language folder based on cookie or browser.

index.php

<?php 
//previous visits will hopefully have lang cookie set. if no cookie, try browser lang
$lang = (isset($_COOKIE["lang"])) ? $_COOKIE["lang"] : substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);

switch ($lang) {
 
	case 'en':
		header('Location:  /en/');
		break;
 
	case 'de':
		header('Location:  /de/');
		break;
 
	case 'fr':
		header('Location:  /fr/');
		break;

	default:
		header('Location:  /en/'); // nothing going. give up use english.
		break;

}
 

?>