You still have to start the services (apache2, mysql). On Debian/Ubuntu installing a server package also automatically enables the service. It's debatable whether this is the right thing to do, but then that's how it is with these distros. You can start the services via YaST also. Also going to
http://localhost/ will get you Directory index not permitted. Try
http://localhost/index.html
There's more you have to do later. You have to enable php5 in Apache if you hope to view PHP pages.