An example of validating Twilio Request with PHP micro framework Slim.

validateTwilioRequest.php

<?php
/**
 * validateTwilioRequest
 * 
 * @param \Slim\Slim $app Slim Object
 * @param Array $params Input parameters
 * @return Boolean Result of the validation
 * @license http://www.opensource.org/licenses/mit-license.php 2014 rutoru
 */
namespace Sample;
 
function validateTwilioRequest($app, $params){

    // Get the request.
    $req = $app->request;

    // Get the X-Twilio-Signature header.
    $twilioSignature = $req->headers->get('HTTP_X_TWILIO_SIGNATURE');

    // Get the Twilio request URL.
    $url = $req->getUrl().$req->getPath();

    // Create Validator
    $validator = new \Services_Twilio_RequestValidator("Your auth token from twilio.com/user/account");

    // Validate
    // *** Important *** Validation needs all parameter, so you have to pass $params to the validate method.
    if ($validator->validate($twilioSignature, $url, $params)) {

        return true;

    }else{

        return false;

    }

}

https://twilio-php.readthedocs.org/en/latest/usage/validation.html

The object "\Services_Twilio_RequestValidator" needs three parameters, $twilioSignature, $url and $params.
Twill Request Validator creates a hash value from all post parameters, so you need to pass $param to the $validator->validate() method with no change.

You can call "validateTwilioRequest" function by this:

<?php
namespace Sample;

require '../vendor/autoload.php'; 

$app = \Slim\Slim::getInstance();
$params = $app->request->params();

$result = validateTwilioRequest($app, $params);