13.10 is no longer supported by the HHVM team, or by Ubuntu/Canonical (see https://wiki.ubuntu.com/Releases)

Are you really sure you want to do this? HHVM 3.0.1 is the last release packaged for Ubuntu 13.10 - there are known security issues in this version (and in other packages in Ubuntu 13.10) - if at all possible, you want to upgrade, even if you're not installing HHVM.

To install prebuilt packages for Ubuntu 13.10 (amd64):

wget -O - http://dl.hhvm.com/conf/hhvm.gpg.key | sudo apt-key add -
echo deb http://dl.hhvm.com/ubuntu saucy main | sudo tee /etc/apt/sources.list.d/hhvm.list
sudo apt-get update
sudo apt-get install hhvm

# If you are getting segfaults
sudo apt-get install hhvm-dbg

If this repo is slow for you, choose a different Mirror.