When you install something with apt-get, it happens that you get prompted with questions like “Do you want to continue [Y/n]?”. You can avoid these, which is nice if you are writing something that will run non-interactively as for example an installation script.
$ sudo apt-get install php5
...
...
...
After this operation, 29.4 MB of additional disk space will be used.
Do you want to continue [Y/n]?
The solution is to add the option -y.
$ sudo apt-get -y install php5
Isn’t this dangerous? Not really. In most situations when you would abort, apt-get will too. You can read more about it in the manual.
This of course works on all Debian based distributions with APT, not just Ubuntu Server.