Over the years, the command for restarting Apache has changed. E.g. here are some:

/etc/init.d/apache2 restart

rcapache2 restart

sudo service apache2 restart

sudo restart apache2

sudo apachectl restart

For even more options see:

http://www.cyberciti.biz/faq/ubuntu-linux-start-restart-stop-apache-web-server/

I finally got fed up of having to work out which option I needed and wrote a simple Mac menu bar app called Mescalero (after the Apache tribe) that lets you restart the Apache web server using a simple GUI. It’s in Beta right now. Sign up to join as a beta user or to be notified once it is formally released here: http://labs.abraxor.com/mescalero/