When running CirrusSearch unit tests under HHVM, the build fails with:
Fatal error: File not found: PEAR.php in mwext-CirrusSearch-testextension-hhvm/src/extensions/TimedMediaHandler/handlers/OggHandler/PEAR/File_Ogg/File/Ogg.php on line 123
We do have the Debian package php-pear installed which install the files under /usr/share/php/. HHVM does not have that directory in its include path whereas the Zend version does:
$ fgrep -R /usr/share /etc/php5 /etc/php5/cli/php.ini:;include_path = ".:/usr/share/php" /etc/php5/apache2/php.ini:;include_path = ".:/usr/share/php"