PHP: How to do caching?

Question

Hi,

So I'm looking to do caching for a forum I'm building and I want to understand the best method. I've been doing some reading and the way that the Zend Framework handles caching (here) explains the idea well, but there are a few things I'm not sure about.

Let's say that I want to cache posts, should I simply "dump" the contents of the query into a file and then retrieve from that, or should I be building the layout around the data and then simply returning the contents of the file? How would I handle user information, historically the standard forum display includes a users total postcount next to a post, this can change (assuming 30 posts per page) very often and would mean I'd have to constantly clear the cache, which would seem pretty redundant.

I can't find any articles about how I should approach this and I'd be interested to learn more, does anyone have any insight or relevant articles to help?

Answer 1

There's always a trade-off between how often you will hit the cache (and hence who useful the cache is) and how much you want to cache and how big the lifetime should be.

You should identify the bottlenecks in your application. If it's the query that's holding the performance back, by all means cache the query. If it's building some parts of the page, cache those instead.

As to retrieving the user posts, if you want that be as live as possible, then you can't cache those (or if you do, you'll have to invalidate all the cached threads where that user has ever posted...). Retrieving post counts from the database (if done right) shouldn't be too taxing. You can just cache a template where the post count is left blank to be filled later or you can do some tricks with Javascript.