The solution we hit on was to leverage Doctrine's system of event listeners to help us do the work. Doctrine allows you to register listeners with the entity manager that are called whenever certain events occur. We created an event listener that is triggered on the onFlush event.

Code is included for the event listener they created - a simple "onFlush" event that grabs the current entities from the manager, sets the date/time property to allow it to be changed (via Reflection) and updating it with the new cleaned format.

Anyhow, one annoying thing about SimpleXML has to do with caching. When using web services, we often cache the contents we get back. We were having a problem where we would get an error about a SimpleXML node not existing.

They were using memcache to store the information but came across problems when their code tried to use a (sometimes) empty tag. He gives two solutions - one using a recursive function that identifies the empty items and the other that encodes then decodes the object to and from JSON, keeping the values intact.