A function to verify Google reCAPTCHA response.

google-recaptcha-verifier.php

<?php
$response=$_POST['g-recaptcha-response'];
$secret='your_secret_key';

 $json=g_rec_verify($response,$secret);


/*
function 
*/
  function g_rec_verify($res,$sec,$ip=null)
  {
  	$post = "secret=$sec&response=$res".$ip!=null ?"&remoteip=$ip":"";
  	$ch = curl_init();
  	$op = array(
  	CURLOPT_URL            => 'https://www.google.com/recaptcha/api/siteverify',
  	CURLOPT_POST           => true,
  	CURLOPT_RETURNTRANSFER => 1,
  	CURLOPT_HTTPHEADER     => array(
                             'Content-Type: application/x-www-form-urlencoded; 
                             charset=utf-8', 'Content-Length: '.strlen($post)),
        CURLOPT_POSTFIELDS     => $post
  	);
  	curl_setopt_array($ch,$op);
  	$gresp = json_decode(curl_exec($ch));
  	curl_close($ch);
   if($gresp->success)
   {
  	return true;
   }
   else 
   {
   return false;
   }
  }
//cheer
?>