Howdy, I've been maintaining a third party Telegrambot plugin which was working for me up to 1 .15 of osTicket.
I just upgraded to 1.18.x and am encountering a strange problem I can't seem to wrap my head around.

When I run the plugin from CLI I am met with the following error:

PHP Fatal error: Uncaught Error: Undefined constant "INCLUDE_DIR" in /var/www/html/osTicket/upload/include/plugins/telegrambot/telegrambot.php:3
Stack trace:
#0 {main}
thrown in /var/www/html/osTicket/upload/include/plugins/telegrambot/telegrambot.php on line 3

Now I know that INCLUDE_DIR is defined in bootstrap.php as follows:

#Get real path for root dir ---linux and windows
$here = dirname(__FILE__);
$here = ($h = realpath($here)) ? $h : $here;
define('ROOT_DIR',str_replace('\\', '/', $here.'/'));
unset($here); unset($h);
define('INCLUDE_DIR', ROOT_DIR . 'include/');

Has something changed in 1.18 that would inhibit a plugin from being able to utilize the variable INCLUDE_DIR?

The Telegrambot plugin just grabs some classes via the require_once expression at the start of the script.

require_once(INCLUDE_DIR.'class.signal.php');
require_once(INCLUDE_DIR.'class.plugin.php');
require_once('config.php');

I know it is a third-party app, and as far as I know the dev has since abandoned it: https://github.com/drtomasso
If anyone is around who has also encountered the same issue since upgrading to 1.18.x and has some tips or tricks, I would be much obliged.

Thank you!