How to prevent caching from web browser?

w0000422 · 01-14-2004, 05:01 AM

hello, i need to refresh the web page everytime the user has reenter the existing URL or clicking on back button...one way to solve this problem is prevent caching from web browser, right.

i had tried the meta type method but this method seem like not very effective for IE.
<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">

then, i tried to use php method to disable the caching feature but come out an error like this:
Warning: Cannot modify header information - headers already sent by (output started at /home/james/public_html/investment/investment.php:1) in /home/james/public_html/investment/investment.php on line 1

Warning: Cannot modify header information - headers already sent by (output started at /home/james/public_html/investment/investment.php:1) in /home/james/public_html/investment/investment.php on line 1

Warning: Cannot modify header information - headers already sent by (output started at /home/james/public_html/investment/investment.php:1) in /home/james/public_html/investment/investment.php on line 1

Warning: Cannot modify header information - headers already sent by (output started at /home/james/public_html/investment/investment.php:1) in /home/james/public_html/investment/investment.php on line 1

<?php
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, max-age=0, must-revalidate"); // HTTP/1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); // HTTP/1.0
?>

does anyone know what i had done wrong?

Guttorm · 01-14-2004, 05:45 AM

Hi

You're doing it right, but the "header" stuff has to be before any other output of the script. The error messages suggests it's in line 1 of investment.php - maybe you're doing this:

<html>
<?php
header...
?>

Change it to:
<?php
header...
?>
<html>
...

and it should work.

w0000422 · 01-14-2004, 06:16 PM

i had used the method u mentioned but i just won't work...

coolman0stress · 01-14-2004, 10:24 PM

your php script must be the very first thing in the file (like Guttorm mentioned). That should work unless you forgot something else. Also adding a "Content-type" header before all other headers would be nice.

Also pragma: no cache is becoming depricated, but i can't think of any other method at the moment.