Custom PHP cache

I have an application that is in need of caching large amounts of data (sometimes even MBs) over multiple page request (for the same user/session). After doing some Googling etc. I've concluded that it is likely best to implement the caching mechanism by writing cache files to disk (please correct me if you think there are better alternatives).

Now, my idea was to have a root cache folder, within which I create folders for each session ID to not overwrite any cached data used in separate sessions. Then for each block of data I will create an unique identifier which can be linked to the data whenever I want to retrieve it again. The data will then be serialized to a string format (using the default PHP 'serialize' function) after which it is written to the appropriate file.

The thing I'm not so sure on how to implement is the clean up of the cached files. At some point either the data is not needed anymore, for example when the session has expired or a number of other reasons. Since it will likely be too much overhead to check for this during each page request, I expect to have to do this externally using some kind of scheduler. However, I cannot guarantee that my application will run on a UNIX environment, so I'd have to consider other platforms as well (Windows, Mac). Is there a general solution that anyone can think of that would be cross-platform without too much hassle?

I'm also thinking that there maybe is a way to intelligently check or mark certain files to be cleaned up, without have to check all the existing files separately. I was considering maybe storing their last accessed timestamp or something, but there may be other criteria besides time that could make the cached data obsolete, such as an exception being triggered in the application (though I could say that whenever that happens the entire cache开发者_StackOverflow for that sessions will be emptied or something like that).

Any suggestions on these issues would be very much appreciated!

If you got MemCache installed, you can use that for caching. It is faster that file cache, and you can give it an expiration time, so it will automatically be removed from the cache after a given period of time.

Both Windows and Unix have scheduled job support - cron for Unix/Linux, and 'at' for Windows. It would be a simple matter to whip up a PHP script to scan your cache directory and apply your deletion criteria to what it finds. Last access timestamp is trivial, basing it on cached file contents or other triggers slightly less so.