A Slack bot that returns a relevant XKCD in response to a /xkcd <search terms> command. It's on the Slack app directory.
Written as a fairly simple Slim application, although pending a rewrite to Lumen (probably) since Slim's dependency injection leaves much to be desired.
There's a cron script at cron/SyncXkcd.php which is run every 10 minutes or so which checks for new XKCD comics and stores them as JSON under storage/.
When a Slack user executes a /xkcd slash command, a POST request is sent to the app with the search terms. The app then searches the locally stored comics for a comic title match. If none was found, it will fall back to searching the web using Bing's search API and return the top result.
If a result is found, it's cached to Redis for future use (and to save my Bing API quota).