Validate Twilio TwilML SMS Request with Laravel (also a Twilio Controller for Laravel)

api.php

<?php
// Place in app/config/api.php
// You'll need to get your TWILIO authToken from https://www.twilio.com/user/account/monitor/getting-started
// and place it in your .env file (or directly in this file, but that's less secure)
return [
    'twilio' => [
        'authToken' => env('TWILIO_AUTHTOKEN')
    ]
];

RequestValidator.php

<?php

/**
 * Twilio Request Validator Class
 * This file goes in app/Models/Twilio (or you can move it around and change the namespace)
 * It requires that you have a file config/api.php
 * Source: https://raw.githubusercontent.com/twilio/twilio-php/3d02ee1f1bde8e860e7dbfd9d2d0d2b7ca7d625c/Services/Twilio/RequestValidator.php
 */

namespace App\Models\Twilio;

class RequestValidator
{
    // You might want to grab the current source for this class from
    // https://raw.githubusercontent.com/twilio/twilio-php/master/Services/Twilio/RequestValidator.php
    protected $AuthToken;

    public function __construct($token)
    {
        $this->AuthToken = $token;
    }

    public function computeSignature($url, $data = array())
    {
        // sort the array by keys
        ksort($data);

        // append them to the data string in order
        // with no delimiters
        foreach ($data as $key => $value) {
            $url .= "$key$value";
        }

        // This function calculates the HMAC hash of the data with the key
        // passed in
        // Note: hash_hmac requires PHP 5 >= 5.1.2 or PECL hash:1.1-1.5
        // Or http://pear.php.net/package/Crypt_HMAC/
        return base64_encode(hash_hmac("sha1", $url, $this->AuthToken, true));
    }

    public function validate($expectedSignature, $url, $data = array())
    {
        return self::compare(
            $this->computeSignature($url, $data),
            $expectedSignature
        );
    }

    /**
     * Time insensitive compare, function's runtime is governed by the length
     * of the first argument, not the difference between the arguments.
     * @param $a string First part of the comparison pair
     * @param $b string Second part of the comparison pair
     * @return bool True if $a == $b, false otherwise.
     */
    public static function compare($a, $b)
    {
        $result = true;

        if (strlen($a) != strlen($b)) {
            return false;
        }

        if (!$a && !$b) {
            return true;
        }

        $limit = strlen($a);

        for ($i = 0; $i < $limit; ++$i) {
            if ($a[$i] != $b[$i]) {
                $result = false;
            }
        }

        return $result;
    }

}

TwilioController.php

<?php

namespace App\Http\Controllers\Shared;

use App\Models\Twilio\RequestValidator;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;

class TwilioController extends Controller
{
    public function postText(Request $request, JenzabarName $jenzabarName)
    {
        $validator = new RequestValidator(config('api.twilio.authToken'));
        if (!$validator->validate(
            $request->header('X-Twilio-Signature'),
            $request->getUri(),
            $request->request->all()
        )) {
            return $this->textError(
                'your request is invalid!'
            );
        }
        $phone = $request->input('From');
        // Do something with the phone number?
        
        $action = explode(' ', strtolower($request->input('Body')));
        $function = "action" . ucfirst($action[0]);
        if (method_exists($this, $function)) {
            return $this->$function($action, $id[0]['ID_NUM']);
        } else {
            return $this->textError('we could not understand your request.');
        }
    }

    public function actionReply($text, $id)
    {
        $this->text('Hello.');
    }

    public function textError($error)
    {
        return $this->text('We were unable to process your request because '.$error);
    }

    public function text($text)
    {
        $xml = '<?xml version="1.0" encoding="UTF-8"?>'."\n".
            '<Response><Sms>'.$text.'</Sms></Response>';
        return response($xml, 200, ['Content-type' => 'text/xml']);
    }

    public function postVoice()
    {
        $xml = '<?xml version="1.0" encoding="UTF-8"?>'."\n".
            '<Response><Say voice="man" language="en">Thanks for calling.</Say></Response>';
        return response($xml, 200, ['Content-type' => 'text/xml']);
    }
}