Add an Attachment to Email Notifications in Ninja Forms

ninja-forms-add-email-attachment.php

<?php
/*
Plugin Name: Ninja Forms Email Attachment
*/

function add_my_attachment( $attachments ) {
     $attachments[] = 'server_path_to_my_file';
     return $attachments;
}

add_filter( 'nf_email_notification_attachments' , 'add_my_attachment' );