Browser Cache with php - Dev Articles

Dev Articles Community Forums Sponsor:

Ajax Application Generator Generate database and reporting .NET Web apps in minutes. Quickly create visually stunning, feature-rich apps that are easy to customize and ready to deploy. Download Now!

December 22nd, 2002, 11:43 AM

wap

Junior Member

Join Date: Nov 2002

Posts: 20

Time spent in forums: < 1 sec
Reputation Power: 0

Browser Cache with php

My index.php page contains latest news taken from a MySql database. The problem I get is as some browsers save the last visited page view, when visitors return any news added doesn't show unless they refresh the page. What is the best way to overcome this problem so a manual refresh is not needed.

Thanks and hope someone can help.

December 22nd, 2002, 01:51 PM

hadley

Contributing User

Join Date: Aug 2002

Posts: 63

Time spent in forums: < 1 sec
Reputation Power: 6

You need to tell browsers not to cache your data with the following http headers

PHP Code:


		
			
 header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");    // Date in the past

header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); 

                                                     // always modified

header("Cache-Control: no-store, no-cache, must-revalidate");  // HTTP/1.1

header("Cache-Control: post-check=0, pre-check=0", false);

header("Pragma: no-cache");                          // HTTP/1.0

(from www.php.net/header)

HTH,

Hadley

December 24th, 2002, 06:01 AM

invoke

Junior Member

Join Date: Dec 2002

Posts: 6

Time spent in forums: < 1 sec
Reputation Power: 0

if hadley's example does not work try this:

PHP Code:


		
			
 header ("Expires: ".gmdate("D, d M Y H:i:s", time())." GMT"); 

header ("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); 

header ("Cache-Control: no-cache, must-revalidate"); 

header ("Pragma: no-cache");

I had all sorts of problems trying to get no-cache to work until I set both expires and last-modified with getdate().

December 24th, 2002, 09:34 AM

wap

Junior Member

Join Date: Nov 2002

Posts: 20

Time spent in forums: < 1 sec
Reputation Power: 0

Thanks for your help guys. I actually cheated a bit and viewed the source code of these forums home page and a solution was there staring me in the face.


<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="no-cache">
<meta http-equiv="Expires" content="-1">
<meta http-equiv="Cache-Control" content="no-cache">


Very similar to your suggestions and I will in fact try them both and add them to my script reference library i am building for personal reference.

Again thanks.

December 24th, 2002, 04:18 PM

hadley

Contributing User

Join Date: Aug 2002

Posts: 63

Time spent in forums: < 1 sec
Reputation Power: 6

It's slightly better to send the no-cache http headers (using the header function) because any proxies along the way will also heed your suggestions. Most proxy caches don't actually parse the html so won't see the http-equiv metadata.

In any case, you only need one or the other, not both.

Hadley

Thread Tools	Search this Thread
Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread: