The vendor folder contains the code for the zingchart-php wrapper.
Each of the url_ prefixed folders contains a demo. Within each folder is a README and an index.php for you to both view the demos and learn how to create drilldown charts with our PHP wrapper.
The most viable demo, in our opinion, is the service layer drilldown but all are acceptable and dependent on project requirements, time and programming abilities.
Questions? Feel free to reach out to us at support@zingsoft.com