Question

How to force webpage not to fetch from cache and directly go to web server

Asked by: shakoush2001

Hi

I got a captive portal program that I setup myself as it was the only one that worked well for my own needs.

It works in the following fashion

Client on LAN --> Gateway with webserver --> Internet


1- User enters office and requests www.google.com
2-Gateway intercepts and redirects to local webserver, the user gets a policy agreement. He presses ok and he gets a message stating that he will get redirected to www.google.com in 5 seconds. However when he gets redirected the browser redisplays the policy page. The same happens if I enter www.google.com into the browser address bar. It works after doing ctrl + F5.

In short I want the browser to get the page from the server and not used the locally cached version.

Thanks

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Asked On
2009-06-12 at 02:34:34ID24486058
Topics

PHP Scripting Language

,

JavaScript

,

Hypertext Markup Language (HTML)

Participating Experts
2
Points
500
Comments
9

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Answers

 

by: MuraliKanthPosted on 2009-06-12 at 02:38:00ID: 24610510

try having empty onunload() method
      window.onunload=function(){}

 

by: MuraliKanthPosted on 2009-06-12 at 02:38:42ID: 24610515

in addition use meta tag to make it no-cache

 

by: shakoush2001Posted on 2009-06-12 at 03:03:40ID: 24610643

Murali where should I add the onunload ?

 

by: hankknightPosted on 2009-06-12 at 06:32:43ID: 24612039

If possible this should be done with PHP.  This code should be at the VERY TOP of your policy agreement page:

<?php
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
if (empty($_GET)) {
$host  = $_SERVER['HTTP_HOST'];
$uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
$extra = '?request=true';
header("Location: http://$host$uri/$extra");
exit;
}

?>

 

by: shakoush2001Posted on 2009-06-12 at 07:00:52ID: 24612345

I did add that and got headers alrady sent out..this is a killer...I did get the code pasted it into notepad++ removed all whitespace then pasted it into vi on the server and saved it and stil lsame error.


Warning: Cannot modify header information - headers already sent by (output started at /var/www/index.php:3) in /var/www/index.php on line 4

Warning: Cannot modify header information - headers already sent by (output started at /var/www/index.php:3) in /var/www/index.php on line 5

Warning: Cannot modify header information - headers already sent by (output started at /var/www/index.php:3) in /var/www/index.php on line 10

 

by: hankknightPosted on 2009-06-12 at 07:06:49ID: 24612415

Show me the first 10 lines of index.php

There may not be any spaces or charactors or anything else in index.php before my code.

 

by: shakoush2001Posted on 2009-06-12 at 07:11:50ID: 24612476

<html>
<head>
<?php
#header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
#header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
#if (empty($_GET)) {
#    $host  = $_SERVER['HTTP_HOST'];
#    $uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
#    $extra = '?request=true';
#    header("Location: http://$host$uri/$extra");
#    exit;
#}
#?>
<META HTTP-EQUIV="Expires" CONTENT="Mon, 06 Jan 1990 00:00:01 GMT">
#<?php
#header( "Expires: Mon, 20 Dec 1998 01:00:00 GMT" );
#header( "Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT" );
#header( "Cache-Control: no-cache, must-revalidate" );
#header( "Pragma: no-cache" );
#?>
<?php
// Date in the past
#header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
// always modified
#header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// HTTP/1.1
#header("cache-Control: no-store, no-cache, must-revalidate");
#header("cache-Control: post-check=0, pre-check=0", false);
// HTTP/1.0
#header("Pragma: no-cache");
?>
<?php $URL = "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']; ?>
<script type="text/javascript">
<!--
function delayer(){
window.location = "<?php echo $URL ?>"
}
//-->
</script>

 

by: hankknightPosted on 2009-06-12 at 07:28:48ID: 24612661

Just as I suspected! There may not be any spaces or charactors or anything else in index.php before my code.

Try this:

<?php
#header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
#header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
#if (empty($_GET)) {
#    $host  = $_SERVER['HTTP_HOST'];
#    $uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
#    $extra = '?request=true';
#    header("Location: http://$host$uri/$extra");
#    exit;
#}
#?>
<META HTTP-EQUIV="Expires" CONTENT="Mon, 06 Jan 1990 00:00:01 GMT">
#<?php
#header( "Expires: Mon, 20 Dec 1998 01:00:00 GMT" );
#header( "Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT" );
#header( "Cache-Control: no-cache, must-revalidate" );
#header( "Pragma: no-cache" );
#?>
<html>
<head>
<?php
// Date in the past
#header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
// always modified
#header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// HTTP/1.1
#header("cache-Control: no-store, no-cache, must-revalidate");
#header("cache-Control: post-check=0, pre-check=0", false);
// HTTP/1.0
#header("Pragma: no-cache");
?>
<?php $URL = "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']; ?>
<script type="text/javascript">
<!--
function delayer(){
window.location = "<?php echo $URL ?>"
}
//-->
</script>
                                              
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by: hankknightPosted on 2009-06-12 at 07:33:54ID: 24612718

Actually, you have too much redundant code! Try this:

<?php
 header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
 header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
 if (empty($_GET)) {
     $host  = $_SERVER['HTTP_HOST'];
    $uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
    $extra = '?request=true';
    header("Location: http://$host$uri/$extra");
    exit;
}
?>
<html>
<head>
<?php $URL = "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']; ?>
<script type="text/javascript">
<!--
function delayer(){
window.location = "<?php echo $URL ?>"
}
//-->
</script>
                                              
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