PHP Registry is meant to store and retrieve key values in files. It can work as a registry that stores application configuration values. The class stores the values in registry values so they can later be retrieved in constants created with the PHP define function. The package also comes with a sub-class that can be used as a Web interface for editing the registry key values. You can set up the keys using the editor class, and then your applications script defines each key as a constant. For instance, it could return your database host address.