Open Terminal and run the following Code: sudo apachectl start
Open your browser and access http://localhost. If it says It Works, then you are set otherwise see if your apachectl has started or not.
Let's make a backup of the default Apache configuration. This will help you to cross check later what you changed or in case you want to restore the configuration to default.
cd /etc/apache2/
cp httpd.conf httpd.conf.bak
Now edit the httpd.conf with vi or any other text editor: vi httpd.conf
Now uncomment the following line (Remove #): LoadModule php5_module libexec/apache2/libphp5.so
Now Restart apache: sudo apachectl restart