400 error when POST data after enabling Csrf, csrfpost_PHP tutorial

public function init(){
  $this->enableCsrfValidation = false;
}

var csrfToken = $('meta[name="csrf-token"]').attr("content");
$.ajax({
 type: 'POST',
 url: url,
 data: {_csrf:csrfToken},
 success: success,
 dataType: dataType
});

  protected function createCsrfCookie($token)
  {
    $options = $this->csrfCookie;
    $options['name'] = $this->csrfParam;
    $options['value'] = $token;
    return new Cookie($options);
  }

  public function validateCsrfToken($token = null)
  {
    $method = $this->getMethod();
    // only validate CSRF token on non-"safe" methods http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.1
    if (!$this->enableCsrfValidation || in_array($method, ['GET', 'HEAD', 'OPTIONS'], true)) {
      return true;
    }

    $trueToken = $this->loadCsrfToken();

    if ($token !== null) {
      return $this->validateCsrfTokenInternal($token, $trueToken);
    } else {
      return $this->validateCsrfTokenInternal($this->getBodyParam($this->csrfParam), $trueToken)
        || $this->validateCsrfTokenInternal($this->getCsrfTokenFromHeader(), $trueToken);
    }
  }