Manual:Short URL/Ampersand semi-friendly solution with root access
From MediaWiki.org
The semi-friendly format is descriptive enough for apache to determine that the index.php script should handle the request. MediaWiki is prepared for this format and obtains the article title directly from the full request information in the $_SERVER hash.
Try transforming the reqested URL to the semi-friendly format of .../wiki/index.php/pagename rather than to the long format of ...wiki/index.php?title=pagename by replacing ?title= with /. For example:
RewriteRule ^(.*[^/])/?$ /index.php?title=$1 [QSA,L]
becomes:
RewriteRule ^(.*[^/])/?$ /index.php/$1 [QSA,L]

