PHP & RSS -- Caching Requests

How to start?

[bofe]

To start, I'm pretty experienced with a lot of aspects of PHP but I've never gotten into caching.

On a lot of sites there's a request of how often you grab an RSS feed. For instance, on Del.icio.us there's this message:

"Please do not poll any single RSS feed more often than every 30 minutes. RSS feeds are not updated more than twice an hour, and you will receive an error if you try to crawl more frequently."

What's the best way to pull RSS feeds and still abide by sites like del.icio.us' terms/requests?

Thanks!

[olwen]

I haven't done this, but I'd write the result somewhere on my filesystem, and only request a new feed if the old one was more than half an hour old.