Small private shopify app

I need to make a small private shopify app in PHP which will read through new shopify orders looking for a specific product and then post details of that order to a seperate API - the system will be run on a scheduler and must keep logs and run with a configuration table to allow it to be added to multiple shopify sites (as a private app) - we will supply a basic setup from an existing app that does a similar (but different) task