class VerifyCsrfToken in Laravel 5.1

<?php

namespace App\Http\Middleware;

use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as BaseVerifier;
use Closure;
use Illuminate\Support\Str;
use Symfony\Component\HttpFoundation\Cookie;
use Illuminate\Contracts\Encryption\Encrypter;
use Illuminate\Session\TokenMismatchException;

class VerifyCsrfToken extends BaseVerifier
{
    /**
     * The encrypter implementation.
     *
     * @var \Illuminate\Contracts\Encryption\Encrypter
     */
    protected $encrypter;

    /**
     * The URIs that should be excluded from CSRF verification.
     *
     * @var array
     */
    protected $except = [
        //
    ];

    /**
     * Create a new middleware instance.
     *
     * @param  \Illuminate\Contracts\Encryption\Encrypter  $encrypter
     * @return void
     */
    public function __construct(Encrypter $encrypter)
    {
        $this->encrypter = $encrypter;
    }

    /**
     * @param \Illuminate\Http\Request $request
     * @param Closure $next
     * @return \Illuminate\Http\Response
     */
    public function handle($request, Closure $next )
    {
        if (
            $this->isReading($request) ||
            #$this->runningUnitTests() ||
            $this->shouldPassThrough($request) ||
            $this->tokensMatch($request) )
        {
            return $this->addCookieToResponse($request, $next($request));
        }

        #throw new TokenMismatchException;

        return Redirect::back()->withError('Sorry, we could not verify your request. Please try again.');
    }

    /**
     * Determine if the request has a URI that should pass through CSRF verification.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return bool
     */
    protected function shouldPassThrough($request)
    {
        foreach ($this->except as $except) {
            if ($request->is($except)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Determine if the session and input CSRF tokens match.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return bool
     */
    protected function tokensMatch($request)
    {
        $token = $request->input('_token') ?: $request->header('X-CSRF-TOKEN');

        if (! $token && $header = $request->header('X-XSRF-TOKEN')) {
            $token = $this->encrypter->decrypt($header);
        }

        return Str::equals($request->session()->token(), $token);
    }

    /**
     * Add the CSRF token to the response cookies.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Illuminate\Http\Response  $response
     * @return \Illuminate\Http\Response
     */
    protected function addCookieToResponse($request, $response)
    {
        $config = config('session');

        $response->headers->setCookie(
            new Cookie(
                'XSRF-TOKEN', $request->session()->token(), time() + 60 * 120,
                $config['path'], $config['domain'], false, false
            )
        );

        return $response;
    }

    /**
     * Determine if the HTTP request uses a ‘read’ verb.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return bool
     */
    protected function isReading($request)
    {
        return in_array($request->method(), ['HEAD', 'GET', 'OPTIONS']);
    }
}