To install hiphop-php on Ubuntu 12.04, add
deb http://dl.hiphop-php.com/ubuntu precise main
to the /etc/apt/source.list
To add the above line in /etc/apt/source.list, you need open it using root user or by using sudo with nano editor.
sudo nano source.list
The file opens in nano editor. Add the above line. Now,
sudo apt-get update
Finally, you can install (or update) your package with the normal apt-get install process:
sudo apt-get install hiphop-php
I hope it helped. Feel free to comment...
References
https://github.com/facebook/hiphop-php/wiki/Prebuilt-packages-on-ubuntu-12.04