protected function validateRequest()
{
$data = $_POST;
$url = $this->url;
$signature = $_SERVER['X-Plivo-Signature'];
$authToken = $this->authToken;
if (!$this->plivo->validate_signature($url, $data, $signature, $authToken)) {
throw new \InvalidArgumentException('This request was not able to verify it came from Plivo.');
}
return true;
}