The Registry pattern provides a mechanism for storing data globally in a well managed fashion, helping to prevent global meltdown.
The goal of the registry pattern is simply to provide client code with a mechanism which allows you to save and retrieve resources across different points of an application. In general creating a basic registry using an object-oriented approach demands that you build a class containing the methods required to perform the saving/retrieval tasks.
A registry is a container for shared objects. In the really basic version, you could use an array. As such, the variable $GLOBALS could be called a registry.