Error handling

When loading a file, exceptions of type XML_XRD_Exception may be thrown. All other parts of the code do not throw exceptions but fail gracefully by returning null, e.g. when a property does not exist.

Using loadFile() may result in PHP warnings like:

Warning: simplexml_load_file( failed to open stream: Connection refused

This cannot be prevented properly, so you either have to silence it with @ or fetch the file manually and use loadString().