php mysql database configuring

I have three ecommerce sites using the same php code and using mysql. Two of the sites shared an API payment gateway. One site had its own gateway which is still operative. The other two sites became inoperative when hosting for the lead site was moved. A copy of the database was not saved. I need a database rebuild and gateway configuration via ssl. I am flexible in regard to data lost or retained. An ealy copy of the database is available however it is not configured correctly. My preferance is for all three sites to share a single database however server security limitations may prevent this. In such a case, it would be good if the description and images of a new product could be populated to each of the three sites and they can still have indepenant databases. If that is too hard, then fully indepant sites is also ok.