Question

The problem is how to do it efficiently when checking whether the cache has expired?

Can you explain with some really basic demo?

Answer 1

There are so many different ways to cache data. You can store them in ram, on disc, etc. I ve wrote my own custom solution that uses memcache/apc/filesystem depending on what I need for the task because I couldn t find one that met my requirements. You can see some examples of caching with PEAR_CacheLite & Zend_Cache. Like hobodave mentioned, apc does have a very simple way of just putting data into the cache with a ttl, but that might not be practical depending on your application. Each of these have some issues, so buyer beware.

Answer 2

Code Sample: checking whether the cache has expired

DEFINE( time_to_live ,60);

 class MyCacheManager {

    function load(key) {
       if(filemtime(/data/cache/key.dat) > time_to_live) {
         //expired!
       }

    }

 }//CLASS

Answer 3

It depends on the case.

The best way is to generate static data, and serve it directly, e.g. via redirect in .htaccess, so the php has nothing to do. Cache expires when your data has changed, e.g. when you add new post (then you generate new static file overwriting old one).

You may want implement two level cache pattern if you need to refresh cache in a specific period of time.

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