We have built a software web-portal (POS system) in PHP language. Which is working fine when online. But when the internet goes down in the stores, the software stops completely and the managers are not able to make bills till the time internet is live again! Hence we want to build an offline module, which involves local server setup (wamp or easy-PHP)and deploying the code offline on the local machine/PC The problem we are facing is syncing the offline and online MySQL databases. Moreover, there are 6 different stores which will be running the offline billing module hence the problem increase here. We want to build a program that can sync both the database offline and online periodically and when the internet goes down and resumes for 6 different stores. Don't know whether this plan is good or not. If not then need guidance on how to crack/tackle this problem! We have used HTML, CSS for design and display, javascript and jquery for client side and PHP for server side programming. We have also used ajax.