a simple service to use Google reCaptcha on Symfony 2.8

ReCaptcha.php

<?php
/**
 * Description of recaptcha service which uses the ReCaptcha API by Google
 * @see https://www.google.com/recaptcha
 * @important Requires a Google account @see https://www.google.com/recaptcha/admin - property "Your property"
 *
 * @version 1.0.3
 *
 * @requires Buzz HTTP library. https://github.com/sensiolabs/SensioBuzzBundle
 * and cUrl (php5-curl), etc.
 *
 * @author Mikel Fernández <mikel.fernandez (at) owasys.com>
 * @copy (C) 2015 Owasys (https://www.owasys.com)
 * @license MIT
 */
namespace MyApp\MyBundleBundle\Services;

use Symfony\Component\HttpFoundation\Request as Request;
use Symfony\Component\DependencyInjection\ContainerInterface as Container;

/**
 * ReCaptcha class
 */
class ReCaptcha {
   
   const API_URL = "https://www.google.com/recaptcha/api/siteverify";

   /**
    * site identifier to use the google recaptcha service
    * this goes into the HTML form like this <div class="g-recaptcha form-control" data-sitekey="{{ google_recaptcha_sitekey }}"></div>
    * @important added to app parameters (to be passed to twig) but not needed for this service
    */
   //private $siteKey;
   /**
    * account identifier (APIKey) for recaptcha API requests
    */
   private $siteSecret;
   private $captchaDisabled;
   private $logger;
   private $container;

   public function __construct($logger, Container $container, $siteSecret, $useCaptcha = TRUE) {
      $this->logger = $logger;
      $this->container = $container;
      $this->siteSecret = $siteSecret; // inject config parameter to this service %site_secret%
      $this->captchaDisabled = !$useCaptcha;
   }

   /**
    * Checks the captcha string against the ReCaptcha service by Google
    * @see https://developers.google.com/recaptcha/docs/verify
    * @param string $captcha
    * @param string $ip
    * @return boolean
    */
   private function check($captcha = '', $ip = NULL) {
      $buzz = $this->container->get('buzz');
      $headers = ['Content-Type', 'application/x-www-form-urlencoded'];
      $toBeSent = array(
          'secret' => $this->siteSecret,
          'response' => $captcha,
      );
      if ($ip) {
         $toBeSent['remoteip'] = $ip;
      }
      $response = $buzz->post(ReCaptcha::API_URL, $headers, json_encode($toBeSent));
      $resp = json_decode($response->getContent());
      return $resp->success;
   }

   /**
    * Check the Google Recaptcha services before processing a public form
    * Log the failed attempts in standard Symfony log
    * @param Request $request
    * @return boolean
    */
   public function captchaIsValid(Request $request) {
      $clientIp = $request->getClientIp();
      //$this->logger->info('before check: '.$request->request->get('g-recaptcha-response'));
      $country = $this->container->get('owasys_web.ip_info_db')->getCityFromIP($clientIp);
      if ($this->check($request->request->get('g-recaptcha-response'), $clientIp) || $this->captchaDisabled) {
         $this->logger->info('Google ReCaptcha ' . ($this->captchaDisabled ? "DISABLED" : "OK") . ' :: client IP ' . $request->getClientIp() . ' (' . $country['name'] . ', ' . $country['region'] . ', ' . $country['city'] . ') :: host ' . $request->server->get('HTTP_HOST') . ' :: UA ' . $request->server->get('HTTP_USER_AGENT') . ' :: lang: ' . $request->server->get('HTTP_ACCEPT_LANGUAGE'));
         //all went well, this client is not a robot or captcha is disabled
         return true;
      } else {
         $this->logger->warn('Google ReCaptcha failed :: client IP ' . $clientIp . ' (' . $country['name'] . ', ' . $country['region'] . ', ' . $country['city'] . ') :: host ' . $request->server->get('HTTP_HOST') . ' :: UA ' . $request->server->get('HTTP_USER_AGENT') . ' :: lang: ' . $request->server->get('HTTP_ACCEPT_LANGUAGE'));
         return false;
      }
   }

}