updates that can happen twice

[Anon]

Is there an easy way to stop people updating twice? - I've got a form which, on a submit, updates a file then writes out to two other files. After submission I direct the user to press a button that sends them to the homepage. The problem is that there is nothing to stop the user from pressing the 'back' button and performing these actions again (and also bypassing my validation).

Any suggestions would be appreciated.

Thanks

Chris

[Anon]

I don't know a quick answer to this problem but I've seen many similar questions posted in this forum. If you search the forum (top right of page) for 'History Back Buttons' I'm sure you'll find plenty of answers!

[[deleted]]

Use the header() function after the form has been processed:

header("Location: homepage.htm");

If that is not enough you can use cookies to remember that the form has been submitted by that browser.

[Anon]

I tried both of your suggestions - thanks.

header() works okay, but they can still 'back' through and update twice.

I then had a (first) go with cookies (I've been thinking about these anyway but wondered whether there was a better way).

Before using them I read a chapter on cookies in my PHP book and I'm pretty sure that I'm avoiding common pitfalls. However, they do not seem to work as I expect.

I set my cookie up in one script (it's on the first line, honest 🙂 ) using default values : -
<?
$updated = 0;
setcookie ("updated", $updated);
?>

I trace $updated in subsequent scripts using echo - it's always 0 until after I update it (obvious I suppose) - trouble is, when I update it to 1 it only seems to stay as 1 in that script - I thought that they were global once set up.

I left the cookie with default values on purpose as I want it to expire when the browser closes.

Am I doing something silly?

Ta

Chris

[stevec123]

why not use the no cache so that they cannot go back
ie
header ("Pragma: no-cache");
header ("Cache-Control: no-cache, must-revalidate");
header ("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header ("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");

I also use javascript to make sure that you can only access the form from a certain page
<!--
function check(){
var from = document.referrer
var here = "http://yourdomain/previouspage.php3"
alert("From:"+from);
alert("Here:"+here);
if (from.substring(0,here.length) != here) history.back()
}
//-->

[Anon]

The no cache idea is very appealing - I have actually managed to get this working using cookies - but I'm not 100% happy 'cos I wanted the server to do everything. I've deliberately steered clear of any browser dependence for the rest of the site.

I had also looked into sessions but I have a deadline looming and don't really have time to experiment.

Thanks for your help, I'll definately give this a go.

Chris