In a new post to his blog Muhammad Hussein Fattahizadeh talks about defining a system that's a bit more handy than the usual one configuration file to one Zend_Config object relationship most projects use. His alternative uses a class to load multiple config files all at once.
The best part of my favorite PHP framework, Zend framework is Zend_Config. With Zend Config you can run you web application with more power full configuration that any one can change your application setting for use. [...] But in most web application you may have many configuration file with special format such as INI, XML or PHP. Also some of configuration is for one part of your application and may you put in special folders.
He includes the code for his class that allows you to start with a base folder and search through it to find ini, xml and php files with configuration information inside. There's also a snippet of code showing how to use it and pull configuration objects from the data it fetches.