Google No-captcha and PHP - php

Question

I am trying to implement the new version of captcha on my website.
What i did so far:
Inside the FORM:
echo '<div class="g-recaptcha" data-sitekey="XXXXXXXXXXXXXXXXXXXXXXXXXXXX"></div>';
Inside PHP:
$recaptcha = $_POST['g-recaptcha-response'];
if(!empty($recaptcha))
{
$google_url = "https://www.google.com/recaptcha/api/siteverify";
$secret = 'YYYYYYYYYYYYYYYYYYYYYYYYYYY';
$ip = $_SERVER['REMOTE_ADDR'];
$url = $google_url."?secret=".$secret."&response=".$recaptcha."&remoteip=".$ip;
$res = getCurlData($url);
$res = json_decode($res, true);
if($res['success'] == 'false')
{
$captcha_error = "Please re-enter your reCAPTCHA.";
}
}
The getCurlData function:
function getCurlData($url)
{
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_TIMEOUT, 10);
curl_setopt($curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.16) Gecko/20110319 Firefox/3.6.16");
$curlData = curl_exec($curl);
curl_close($curl);
return $curlData;
}
What i want to achieve is to distinguish when the no-Captcha box is checked. I want to throw an error to the user if he/she did not check that box.
So far i only throw an error if the response from Google is "We are not sure if you are human, please proceed to our second level of verification" [if($res['success'] == 'false')].
PS: most of the code is written by Srinivas Tamada. You can find it here.
Thanks in advance.

Answer 1

The response is a JSON object:
{
"success": true|false,
"error-codes": [...] // optional
}
https://developers.google.com/recaptcha/docs/verify
If you parse that JSON you will get something like this:
object(stdClass)[1]
public 'success' => boolean false
public 'error-codes' =>
array (size=1)
0 => string 'missing-input-response' (length=22)
So if response contains an error code with 'missing-input-response' you can tell that user didn't click on checkbox.
I implemented No Captcha without curl in small library I wrote recently, so you can check it out if you want more details:
https://github.com/zoran-petrovic-87/ZorAuth
http://zoran87.blogspot.com/2014/12/zorauth-10b-complete-flexible-no.html