我知道了:

RewriteEngine on
RewriteRule ^language/(.*)$ index.php?l=$1

现在，我可以打开类似 http://example.com/foo/bar/language的URL /de/，但浏览器会加载 http://example.com/foo/bar/index.php?l = de

Now i can open URLs like http://example.com/foo/bar/language/de/ but the browser loads http://example.com/foo/bar/index.php?l=de