$ sudo /usr/bin/update-alternatives --install /usr/bin/php php /usr/bin/hhvm 60

$ sudo apt-get remove hhvm
$ sudo /etc/init.d/apache2 restart

$ sudo /usr/bin/update-alternatives --remove php /usr/bin/hhvm
$ sudo /usr/share/hhvm/uninstall_fastcgi.sh
sudo: /usr/share/hhvm/uninstall_fastcgi.sh: command not found
$ sudo /etc/init.d/apache2 restart