how to get g-recaptcha-response from old recaptcha ?

I am striving with recaptcha for some time trying to get aforesaid parameter transferred to server side.While it works in case of the new reacptcha (with checkbox "I am not robot")It does not work in case of the good old recaptcha: for example based on this onehttp://www.google.com/recaptcha/demo/What's up ?What wrong I do ?How to obtain the parameter's value in a case the old version in use ?I would like to check it on server side. -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.