Never flown into PHL before and was wondering what the situation is regarding flight transfers.

We are flying in from LHR with a transfer on to SJU both flights with US Air. The connection is shown as being 2 hours 15 minutes. Am I correct in saying that we will have to check our luggage in as if we had just arrived kerbside and go back airside after clearing security. Finally will the 2 hour 15 minute transfer between the flighs be enough?

Thanks in anticipation

Paul