Using External Code in a Plugin

Hello,

I am using the Website Comments plugin and currently users can upload files with their posts. The files are uploaded to the app server however I would like to upload the files to S3.

We already have the S3 file upload functionality working well in other areas of the site. The main file is at /cmsb/lib/s3_functions.php

So I would like to include this file in the websiteComments.php code but when I try the following it does not work:

include_once(__DIR__ .'/../../lib/s3_functions.php');

I receive this error:

#85 - UNCAUGHT_EXCEPTION: Credentials must be an instance of Aws\Credentials\CredentialsInterface, an associative array that contains "key", "secret", and an optional "token" key-value pairs, a credentials provider function, or false./var/www/html/php/dev/cmsb/vendor/aws/aws-sdk-php/src/ClientResolver.php (line 419)http://dev.test/bulletin_board.php

I'm not sure why we are able to upload to S3 on normal "list" and "detail" pages but can't get this to work when used in a plugin. Is there something like a hook that needs to be written?

If anyone could offer some advice that would be great!

Thank you,
Greg