DokuWiki will run just fine with Darklight and PHP through CGI.

Ensure the stage2 handler for your site's root directory includes php, and that the stage1 handler for the data, inc, bin, and conf directories is set to none. Your hosts.conf entry should look something like:

site wiki.example.com http {
        root /srv/web/wiki.example.com/htdocs index.php ok php,default
        path data index.php none none
        path conf index.php none none
        path inc index.php none none
        path bin index.php none none
}

You may also need to set the cookiedir setting in DokuWiki's conf/local.php before user logins will work.

$conf['cookiedir'] = '/';