Rasmus, thanks a lot!! Your information has been very helpful because now I
know more ways to play with the headers!.
Still, I am almost sure that it's possible to do what I want to do because I
think I've seen such behaviour in other websites, for example Yahoo! Mail
(note that the site does not have to be programmed in PHP because we are
talking about then client behaviour, not the server's).
Thanks a lot again, I am sure with your information I'll be able to work it
out... and then I'll post the solution here!
Cheers, Diego.
-----Original Message-----
From: Rasmus Lerdorf [mailto:[EMAIL PROTECTED]]
Sent: Thursday, 19 April, 2001 8:34 PM
To: Diego Fulgueira
Cc: Php-General
Subject: Re: [PHP] Cache Control with forms
> Hi everyone! I have the following problem:
> I don't want any of my site's pages to be saved on any browser's cache.
> Yet, I want all HTML forms to keep their data when the user changes to
> another page without submiting and then comes back using the back button.
>
> I have seen changing the session.cache_limiter configuration option to
> 'private' instead of 'nocache' works to make all forms keep their data,
but
> then all pages are diplayed from the browser's cache even after refreshing
> several times!. I want a point in between, but I don't know how to get
> there.
>
> By the way, do you know what do the values that session.cache_limiter can
> take mean? (nocache, private and public)
When you set it to 'nocache' you get a set of HTTP headers that look like
this:
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0,
pre-check=0
Pragma: no-cache
That forces things to not be cached anywhere.
The 'private' setting sends these headers:
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: private, max-age=10800, pre-check=10800
The expires header is set to a time in the past to force non-HTTP 1.1
compliant caches not to cache the page. For HTTP-1.1 caches that
understand the cache-control header the page will be cached only in
private caches (ie. the end-user http-1.1 compliant browser) for the time
specified by the session.cache_expire setting.
The 'public' setting sends headers like this:
Expires: Thu, 19 Apr 2001 20:57:16 GMT
Cache-Control: public, max-age=10800
Basically this means that the page is allowed to be cached in both public
(like AOL's proxy-cache) and private caches for the time specified by
session.cache_expire
And no, I don't know of a way to do what you want. I don't think you can
have the back button working and at the same time not allow private
caching.
-Rasmus
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