I have a php program that has been written keeping in mind a single server, so there are inherent limitation to how much it can handle. For example, the developer says that his current webhosting service provides him with "50 mysql connections" which he interprets as that only 50 people can be simultaneously logged onto it.

What do we need to do if we want to scale it up so it can handle a load of 500 or more? How can we adapt this program to a "load balancer" with minimal changes?

The application is writen in php and uses mysql.