Error with mondatry webhooks in publich app

Hello Everyoone,

I am stuck while publishing a public app to shopify, basically i just wanted to know after giving the three webhooks url to the app setup what should i code their.. I have created three files on same server with php and given same link to app setup for all three mandatory webhooks, now i need help to what code i have to add, i mean what type of code and how to validate?