Unable to integrate reCAPTCHA

I am a newbie and I have no idea on how to do this... I did the two steps, one on client & server side... but I am not sure where to put this code is_valid) {    // What happens when the CAPTCHA was entered incorrectly    die ("The reCAPTCHA wasn't entered correctly. Go back and try it again." .         "(reCAPTCHA said: " . $resp->error . ")");  } else {    // Your code here to handle a successful verification  }  ?> I have a contactform.php in my website folder and I pasted that above code on line 2 but it din't worked... where should I paste the above code in my contactform.php?? -- 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.