Comment 7 for bug 179803

you can install the package this way
https://launchpad.net/~mapopa/+archive

sudo vim /etc/apt/sources.list

add these lines
deb http://ppa.launchpad.net/mapopa/ubuntu gutsy main
deb-src http://ppa.launchpad.net/mapopa/ubuntu gutsy main

sudo apt-get clean
sudo apt-get update
sudo apt-get install php5-interbase