I have installed xampp to Ubuntu 12.04. I have put my project in the folder /opt/lampp/htdocs/project_is_here
When I type in the browser localhost/soap/php
localhost/soap/php
I had given all the permission , still got the error message. Go to -> /etc/apache2/sites-available/000-default.conf set : DocumentRoot to /opt/lampp/htdocs
All solved for me. Change the "DocumentRoot" to whichever folder your project is.