New on the Zend Developer Zone today there's a post that looks at working with the Zend_Registry component of the Zend Framework and how deleting the index out of it directly could be a bad thing for your application.
Zend_Registry is the implementation of the Registry design pattern in the Zend Framework. It is similar to the $_GLOBALS array in pure PHP , but unlike it, it does not provide a transparent way to unset values at a specified index. As you will see in this short article, there is a very simple way to do it, but that doesn't mean it should be done.
He advises against directly using the "_unsetInstance" method that the component provides to remove items from the registry but that could cause unwanted side effects with your data. Instead he recommends using the SPL ArrayObject interfaces and the "offsetUnset" method on the registry instance to drop the item. He ends with a word of warning, though - be careful what you remove in one part of your application because something, somewhere might be depending on it being there, set or not, to make another decision.