Type aptitude
to start the package manager. There you can see which applications are installed.
Use /
to search for packages. Try searching for apache2
and php5
(or whatever versions you want to use). If they are installed, they should be bold and have an i
in front of them. If they are not installed (p
in front of the line) and you want to install them (and you have root permissions), use +
to select them and then g
(twice) to install it.
Word of warning: Before doing that, it might be wise to have a quick look at some aptitude tutorial on the web.