If you are not getting a package on Ubunu using apt-get then chances are that it has not been updated in the /etc/apt/sources.list file
For example, the following should be there in the sources.list file if you are running Ubuntu 10.04 LTS (codename lucid)
## main & restricted repositories deb http://us.archive.ubuntu.com/ubuntu/ lucid main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ lucid main restricted deb http://security.ubuntu.com/ubuntu lucid-updates main restricted deb-src http://security.ubuntu.com/ubuntu lucid-updates main restricted deb http://security.ubuntu.com/ubuntu lucid-security main restricted deb-src http://security.ubuntu.com/ubuntu lucid-security main restricted ## universe repositories - uncomment to enable deb http://us.archive.ubuntu.com/ubuntu/ lucid universe deb-src http://us.archive.ubuntu.com/ubuntu/ lucid universe deb http://us.archive.ubuntu.com/ubuntu/ lucid-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ lucid-updates universe deb http://security.ubuntu.com/ubuntu lucid-security universe deb-src http://security.ubuntu.com/ubuntu lucid-security universe
[…] PHP, PHP5, phpMyAdmin, Ubuntu, Ubuntu 10.04, Ubuntu 10.04 LTS, Ubuntu Server If you are not getting a package on Ubuntu, please check to see if your /etc/apt/sources.list file is updated. This is common with most VPS […]