yes the first thing that happened to when I tried to connect joomla page to database was this line. and I couldnt figure our what happened until I realized that I cant make a raw php page and make a connection to database usually I should set all php into the controller.php for the component in a function and if I want to request that function the URL should go in something like :

http://localhost/joomla/index.php?option=com_user&format=raw&view=register&task=user_availability

- option is the current component
- raw is to request a plain page without the template design
- view : is what you are currently viewing
- task : is the function from the controller you want to run