This DokuWiki installation was extended to support multiple languages. By default, the wiki uses either the language of the visitor, if possible, or German, if either the browser does not send an "accept language" header or the list of accepted languages does not contain any of the valid wiki languages.
The idea is described in tips:multilingual_content. Generally, i used the suggested changes as described in tips:multilingual_content:local.php. Additionally i changed a number of things:
The page names and the "You are here" header are displayed without the language as namespace
An Apache rewrite rule redirects a number of the previous namespaces to the default language, so existing URLs are still valid
Additional links in the header to change the language
The search form and the "live" search for matching pagenames has an additional parameter for the current language
Note: English is not my mother tongue - therefore not all pages are available in English and the existing translations may contain errors - but at least it should be understandable