How to make one step Human Verification like in StackOverflow?
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/1465704/php-captcha-without-session">PHP Captcha without session</a>  </p>
</blockquote>



<p>That after I send a form I get to captcha page - than I go back to the form?
How to do it?
Should I use session?</p>

<p>I know how to implement captcha on form page 
but I wonder how it's done:
that I get redirected to verification page ex. <a href="http://stackoverflow.com/captcha?s=f689274e-e760-482d-a008-31d4bd469f80">http://stackoverflow.com/captcha?s=f689274e-e760-482d-a008-31d4bd469f80</a></p>

<p>I don't need any specific explanation - I would like to get an idea.</p>
