Imagine that users with question searching in MediaWiki.org would obtain results of https://discourse-mediawiki.wmflabs.org/ as well. Wouldn't that be useful? Now imagine that this Discourse forum would contain not only technical questions, but also the archives of our technical mailing lists. Wouldn't that be very useful, and awesome?
See how others have integrated Discourse search results in WordPress (another PHP application).
Maybe this could be a project for an internship or a contractor?