Stop FIREFOX from captcha caching

Question

So, I have this form here: http://www.piataterenuri.info/register.php The problem is that Firefox caches the captcha image, and after entering the introduction, or refreshes the page. Captcha will display the old image instead of the current one.

I have already posted:

header("Cache-Control: no-cache");
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");

And also changed captcha img src to

<?php $rand=microtime() * mktime(); echo "src=\"captcha.php?time=$rand\""; ?>

What else can I do to stop caching Firefox images?

Answer 1

Correct this one Last-Modified: Tue, 12 Oct 2010 18:11:57 GMT. Send the current time to the header Last-Modified.

Answer 2

force ffx ajax