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From: Twayne <nobody@spamcop.net>
Newsgroups: comp.lang.php
Subject: Re: Please evaluate my cache-control & pragma etc. code
Date: Sat, 10 Aug 2013 13:21:24 -0400
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On 2013-08-10 4:49 AM, The Natural Philosopher wrote:
> On 09/08/13 19:22, Twayne wrote:
...
>> <?php
>> session_start();
>> header('Cache-Control: no-cache, no-store, must-revalidate'); //HTTP/1.1
>> header('Expires: Sun, 01 Jul 2005 00:00:00 GMT');
>> header('Pragma: no-cache'); //HTTP/1.0

...

> my limited experience suggests that browser caching is more affected by
> the etag.
> I have been writing a framework that serves all pages /objects from a
> database ( for reasons of security and control), and found that in
> general browsers don't really honor cache control, but they do honor etags.
> I think proxies tend to honor cxahche control more.
>
> The browsers tend to say 'ive got a copy, do I need a new one?' and
> actually ask, using the etag.
>
> I found that out looking at my log files  on pages with multiple images
> under constant  rerfreshing. The logs were full of 304 responses, but
> there were always as many of those as the page had images for a given
> page load.
>
> The code that checks the etag is here - it really does reduce server
> load if you want to not resend data that's already been sent
>
> // check if etag matches if none match request headers
> function check_etag($etag)
>      {
>      if(isset($_SERVER['HTTP_IF_NONE_MATCH']) &&
> strstr($_SERVER['HTTP_IF_NONE_MATCH'],$etag))
>          {
>          header('HTTP/1.0 304 Not Modified');
>          exit();
>          }
>      }
> This is a handy way to encourage browsers not to re-download static pages.
>

Which is precisely what I want to do, actually.  I'll look into that a 
bit further and try it! Thanks much for the alternative.

Best regards,

Twayne`