Payfast payment gateway ITN request not working in Laravel 5.1

I have integrate payfast payment gateway in our Laravel 5.1 website, it is working perfect on our development server but when we move site on live server it give error in ITN request step, here is the error which I am getting:

HTTP/1.1 500 Internal Server Error
Date: Wed, 09 Nov 2016 14:10:09 GMT
Server: Apache
Cache-Control: no-cache, private
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

When I am searching for solution I got below option to enable ITN request without CSRF token

protected $except = [
//
'/itn'
];

but this also not working, I put sample code folder on my website root folder and try to do payment and that will working.

Also when I try to write notify response in text file it print success in response to the file.

via Chebli Mohamed