Re: How does caching work?

On Tue, Jun 9, 2009 at 16:35, Paul M Foster<paulf@quillandmouse.com> wrote: > > But if a page is populated with variables from a database (for example) > which could change from time to time, how could a caching engine > possibly cache it? How would it determine whether to re-fetch the page > or use the cached version? This is more a matter of the HTTP protocol and HTML standards. Check into meta (pragma) 'no-cache' tags and Google "cache control" for the basics on this. Thankfully, (at least most) clients do not check the full page to see if there's an updated version --- because if they did, they may as well display it, as they'd use up the network, server, and a portion of the client resources in doing so. Instead, they check the cache expire time and/or compare the local (cached) copy against the timestamp of what the server says for the file's "last-modified" stamp - known as a file's 'mtime' data. If I've somehow circumlocuted your question, ignore me and pretend I was never here. ;-P -- </Daniel P. Brown> daniel.brown@parasane.net || danbrown@php.net http://www.parasane.net/ || http://www.pilotpig.net/ 50% Off All Shared Hosting Plans at PilotPig: Use Coupon DOW10000