E-commerce site

Hello in my job , my boss want me to create solution for any one purchase ebooks from our site can get access to our online courses by answering questions , so coz we use some plugins of membership , i succeed to create 20 forms (each form for each book for make our members can get access to any course relied to that book , ) , so my question i’m scared that my solution is not plugin it’s a simple php files works when i put require (load.php) and use some hooks of wordpress , i will add thoses files on our folder of wordpress , and we used linux as system of servor ,is that can made errors like 500 error , i ‘m glad i find solutions but still scare about any technical error can be ,this link of my code https://gist.github.com/AladinDridi/6f41e94c70fabf9e15726634fb9a967b,
wish any advice from you can help , thanks