Manual:$wgSearchForwardUrl

Details
Set this to a URL to forward search requests to some external location. If the URL includes ' ', this will be replaced with the URL-encoded search term. For example, to forward to Google you'd have something like: $wgSearchForwardUrl = 'http://www.google.com/search?q=$1'. '&domains=http://example.com'. '&sitesearch=http://example.com'. '&ie=utf-8&oe=utf-8'; NOTE: From versions 1.4.8 to 1.4.15, this setting was incorrectly named $wgForwardSearchUrl in DefaultSettings.php. If you are using one of those versions then this alternative name should be used instead.