How to show the available version of a package (before doing apt-get install)

To show the version of the package that will be installed with apt-get install, do apt-cache policy packagename. To show the currently available version(s) of PHP5, do:

apt-cache policy php5

This article was written quite a while ago (7 years), please keep this in mind when using the information written here. Links, code and commands might be outdated or broken.