Simple reCAPTCHA PrestaShop contact form controller override

ContactController.php

<?php

class ContactController extends ContactControllerCore
{
    public function postProcess()
    {
        if (Tools::isSubmit('submitMessage')) {
            $response = $_POST["g-recaptcha-response"];
            $url = 'https://www.google.com/recaptcha/api/siteverify';
            $data = array(
                'secret' => '_YOUR_SECRET_',
                'response' => $_POST["g-recaptcha-response"]
            );
            $options = array(
                'http' => array (
                    'method' => 'POST',
                    'content' => http_build_query($data)
                )
            );
            $context  = stream_context_create($options);
            $verify = file_get_contents($url, false, $context);
            $captcha_success=json_decode($verify);

            if ($captcha_success->success==false) {
                $this->errors[] = Tools::displayError('Captcha error.');
            } else {
                return parent::postProcess();
            }
        }
    }
}