Input on caching methods?

I'm starting to work on caching for my application and I'd appreciate some input.

Some facts about my site (www.danceminder.com):

1. It's fairly dynamic but doesn't change that frequently.  Yet. Once I allow more users editing access I expect that to change.
2. There are two main views for dances.  Crib or Full which completely changes the look of the page.  Even though the look changes, the underlying structure doesn't.  There's a Dance, one or more Figures and for each Figure there are one or more Movements.
3. Every element of a dance is time-stamped so I know exactly when it was last changed.
4. The pages are presented slightly differently depending on who is viewing the page.  If it's a non-logged in user they don't get all the information and/or menu links change.  If they're an editor or admin, the menus change even more. So I may or may not want to cache the menus.  Or I might.

I'm currently thinking that I can get away with caching Dance/Figure/Movement output independently.

I'm also thinking that I might need a cache-key table in the database so I can keep track of when a cache entry was last updated and use very long expire times so that rather than the cache expiring based on time, I regenerate it based only on need.

I may also need to trigger a cache update if view or css code changes.  I don't want to invalidate the entire cache but that may be the simplest method for now.

Any particular thoughts or feedback?  I haven't implemented caching in a PHP app before so any info is welcome.

Are you trying to cache the views or the data?

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