After looking over the Mediawiki chat extensions[1] and failing to get any of those for IRC to work in MediaWiki 1.11.0, I grabbed the extension template[2] and created my very first MediaWiki extension.

To get the extension to work, complete the following steps:

1. Open IRC_body.php. Search and replace "irc.example.com" with the IRC network address you wish to connect to.
2. In IRC_body.php, globally search and replace all "example.com" with your domain name.
3. In IRC_body.php, globally search and replace all "#example" with the name of your IRC channel.
4. Open IRC.i18n.php. Search and replace "Example chat" with the title of your English chat page.
5. In IRC.i18n.php, search and replace "Beispiel-Chat" with the title of your German chat page if applicable. Add any additional languages you might require.
6. Upload IRC.i18n.php, IRC.php, and IRC.php to /extensions/IRC/.
7. In the code subdirectory, edit or replace background.gif if applicable. Your background.gif should generally not exceed a size of 350*350 pixels.
8. Upload the code subdirectory to /extensions/IRC/code/. This subdirectory contains PJIRC.
9. Add the following line to the end of your LocalSettings.php (i.e. as last line or just above "?>"):

   require_once( "$IP/extensions/IRC/IRC.php" );

The name of the chat page as specified in 4. above is now available in your list of special pages and you can link to it with [[Special:IRC|Example chat]]. I usually configure PJIRC reasonably novice-proof. From my experience, users that rely on PJIRC tend to desire easy chat access and get confused by overly complex applications. You will notice that in the sample configuration, users cannot leave the designated channel and get to use the simplest PJIRC window. Obviously you can adjust the PJIRC settings, please refer to the documentation included in the PJIRC package.

Last but not least, please refer to this post detailing a workaround for the expired PJIRC certificate.

PS: This extension does not work in MediaWiki 1.11.1.

References