On the Zend Developer Zone there's a new tutorial from Vikram Vaswasi about working with the configuration data from your files (in multiple formats like XML and the more traditional INI) with the help of the Zend_Config component of the Zend Framework.
Thus far, I'd been using a hand-rolled library for this task; however, this library was now fairly dated and didn't take advantage of many of the newer PHP 5.x features and so, I'd been looking for a more modern replacement. Zend_Config seemed to meet my needs, so I played with it a little and then deployed it in a couple of projects. It did everything I needed it to, and was easy to integrate with both framework and non-framework PHP projects. It also has a couple of neat features, such as the ability to merge multiple configurations together.
His "crash course" starts with an example of pulling in the contents of an XML-based configuration file with dialer information (like for a modem). He talks about setting up rules, formatting the results, working with more complex nested data and much, much more. The Zend_Config component allows you to be hugely flexible with how you handle - and translate - the data that comes out of your config files.