image stays in memory? (image verification script, when refreshing the page...)

[dsaba]

i have an image verification script that I use on a form

it works fine, and displays a random string on an image

 

the problem is when I link back to the page the last image code still shows, when in fact a new code has been generated, i have to refresh the page to actually get the image to change

 

this also happens when i press the back button to go back to the page as well

 

so what I need to know is: is there a way to not keep this image in the browser's memory, and force it to truly show the new image that the script produces?

 

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

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

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

 

but it doesnt' help, I appreciate some help, my script is way to complicated to post, if you need more explaining on the situation I can do that - thanks

[per1os]

You can set a session variable on the "wrong" page that states $_SESSION['resetimage'];

 

If that variable is true, re-generate the image in the script.

 

I am not sure if it will work, but give it a try see what happens.

[dsaba]

damn this is really hard to explain and i'm usually pretty good at doing that

 

let me just show you what I mean go to this link:

http://p2mhunt.awardspace.com/submit.php

 

there you will find a form asking you to login, all you need to do is fill in the verify code field

 

if u fill in the wrong code it will alert you and tell you that it is the wrong code

 

now if you're very keen you will notice that the "session code" is different than the code it originally asked you to type, this may seem like an error but it is not, I know this because when it brings you to this "wrong image verification code page" it re-makes the session and image code so it will be a different code

 

so you know what the image below is supposed to show it tells u the newly generated code

but if you look below you will still see the old image

[per1os]

Yea, I understood the problem. I do not think there is a fix out there. If you look at (I think) even google has that issue in gmail if you mistype your password a few times.

 

Anyhow if someone else knows I am sure they will enlighten us.

[dsaba]

no when you sign up for a new user in yahoo

and when u get the image code wrong and you press teh back button on the browser

you will see a NEW image verification code

 

so it can be done, i know yahoo uses cgi, but slashdot.org does as well

[anita999]

Try looking at http://www.white-hat-web-design.co.uk/articles/php-captcha.php

 

There is a good example there and I think it is using a jpeg image like you.  It refreshes everytime.  Look at CaptchaSecurityImages.php and it might help.

[dsaba]

thanks that code is helpful on that webpage

 

however- it basically is just yet another method or script that displays a captcha like image verification, which was not my problem, improving my image verification script was not the goal

 

the goal was how to get it to refresh automatically all the time

 

from reading that other script on that webpage this is what I gather:

1. imagejpeg($image); they output the image directly to the browser

2. on my script I do this imagejpeg($image, "verifycode.jpeg"); so a picture file actually physically resides on the domain

 

 

could anyone shed some truth to my hypothesis of doing step #1 as the only way to get it to automatically refresh???

[calabiyau]

<img src="verify.png?time=<?php echo $time;?>"/><br/>

 

do this where you call the verification image and let $time be somewhere up the page equal to a unique value like time().  This unique parameter attached to the image will force the browser to download the new image instead of using cached one.