Testing ReCaptcha Dynamically?

I've got recaptcha working in it's fundamental form - requiring a captcha code and displaying a basic error when it's wrong. But I want to make it more usable, and I'd really appreciate your help.

Is there any way to ajaxically send a test/request to see if the captcha code is correct, and if it's not, pre-emptively prompt the user for another attempt?

Failing that开发者_开发技巧 possibility - is there any way to ensure that all the fields keep their values if I were to php redirect the user back to the form page?

Thanks!

reCAPTCHA has an AJAX API as described here.

You need to include the script in your page:

<script type="text/javascript" src="http://api.recaptcha.net/js/recaptcha_ajax.js"></script>

And then define a callback to fire when it gets the response:

Recaptcha.create("6LdIEwAA......",
  "recaptcha_div", {
  theme: "red",
  callback: Recaptcha.focus_response_field
});

There's a demo of it working here.