some week in the future i will have job to create php web app that will work as billing process. As the client and my team agree upon, the web app will only deploy in their internal server. This need arose some fundamental questions for myself.

1. how do we lock the web app really really will work only in internal server and not in internet as it asked ? cause this need, the cost for the job have been cut into some degree. so it will be best if it only work as client describe it : it will be deploy in intranet an intranet only
2. What is the pro and cons deploy php application only (with all of its apache server )in intranet ?
3. What is the fundamental different between deploying php app in intranet environment and in internet ? is there anything to be consider ?
4. I know we can put windows in to a flash-disk or pen-disk. i there any autorun apache/php server that work in the same fashion ?