Recaptcha for existing form ... the php part is giving me problems

Question

Am not really a coder, but understand a little... Bought a web template with a contact form. It sends the form to a php for validation, which in turn sends it to me in an email. I can get the Recaptcha to appear fine on the form... But the php seems to fail (gives me a 500 error, but it DOES send out the form email to me)... Sorry... I'm tearing my hair out!

The following is the php file:

$response = $_POST["g-recaptcha-response"];

$url = 'https://www.google.com/recaptcha/api/siteverify';
$data = array(
    'secret' => 'secret_code_here',
    '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 ($captcha_success->success==false) {
    echo "<p>You are a bot! Go away!</p>";
} else if ($captcha_success->success==true) {

use VanillaForm\MailSender;
use VanillaForm\Utils;

require_once('inc/Utils.php');
require_once('inc/MailSender.php');




header('Access-Control-Allow-Origin: *');




  /*
   * Check if call is a POST request (data was sent by form).
   * While it's not a POST request it returns OK, which can be handy with checking that the script is alive.
   */
  if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
      if (function_exists('mail')) {
          die('OK');
      } else {
          die('PHP parser works, but <b>mail()</b> function seems to doesn\'t exist');
      }
  }

  /*
   *
   * Vanilla Configuration starts HERE
   *
   */
  $vf_config = array(
      /*** Code Snippet - quick-start ***/
      /**
       * Recipient's e-mail. To this e-mail email will be sent.
       * E.g. Single recipient
       * 'emailRecipients' => '[email protected]',
       *
       * E.g. Multiple recipients
       * 'emailRecipients' => '[email protected], [email protected]',
       */
      'emailRecipients' => '[email protected]',

      /**
       * If is not empty it sets a header From in e-mail message (sets sender e-mail).
       * Note: some hosting servers can block sending e-mails with custom From field in header.
       * If so, leave this field as empty.
       * E.g. Single recipient
       * 'emailSender' => '[email protected]',
       */
      'emailSender' => '[email protected]'
      /*** /Code Snippet - quick-start ***/
  );
  $vfSender = new MailSender($vf_config);

  /*
   * Some variable may need translation for better readability.
   * You can access and modify variables by:
   * $vfSender->data['variable-name']
   */
  switch ($vfSender->data['gender']) {
      case "F":
          $vfSender->data['gender'] = "Female";
          break;
      case "M":
          $vfSender->data['gender'] = "Male";
          break;
      default:
          $vfSender->data['gender'] = "Not selected";
          break;
  }

  // Define here subject of the e-mail message
  $subject = 'Website Contact Form - New Message from '.$vfSender->data['name'];

  // Define here content of the e-mail message
  $content = "Hey,
  You've received new message from your website. Check the details below:

  Sender's IP address: ".Utils::getIp()."
  Name: {NAME}
  E-mail: {EMAIL}
  Phone number: {TEL}
  Subject: {SUBJECT}
  Message:
  {MESSAGE}
  ";

  // Set subject and message content
  $vfSender->setMessage($subject, $content);

  /*
   * Vanilla Configuration ends HERE
   */

  die($vfSender->sendMessage());



}