I found this site when I search the way to install Apache as webserver and PHP5 on my Ubuntu 10.10.
sudo apt-get install apache2
sudo apt-get install php5
sudo apt-get install libapache2-mod-php5
sudo /etc/init.d/apache2 restart
One said that you don’t need to run sudo apt-get install libapache2-mod-php5 command because it is done with sudo apt-getinstall apache2.