Thread:Project:Support desk/New Install Environment Variables

I'm performing a fresh install from the following instructions.

Manual:Running MediaWiki on Ubuntu

I can't help but feel like I am missing some environment variables. I get the following error when adding the Knowledgebaseextension.

Warning: require_once(SpecialPage.php): failed to open stream: No such file or directory in /var/www/mediawiki/extensions/SpecialKB/SpecialKB.php on line 24 Fatal error: require_once: Failed opening required 'SpecialPage.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/mediawiki/extensions/SpecialKB/SpecialKB.php on line 24

Then when I manually specify the location in the SpecialKB.php file, I get another error:

Fatal error: Call to undefined method SpecialPage::addPage in /var/www/mediawiki/extensions/SpecialKB/SpecialKB.php on line 35

What am I missing in these install instructions?

Thanks