I'd like to understand how Drupal core works by tracing core logic and how functions unfold. I installed Netbeans with xdebugger and started a new project. The project includes drupal installation run on localhost. I read several Netbeans quickstart manuals and began studying core by putting breakpoints. But when I start debugging the project they do not seem to work. Please explain any productive approach for studying drupal 7 core logic using Netbeans with Xdebug?