If the connection you book in PHL is long enough that you could realistically claim your bag, re-check it, and re-enter security, just ask the check-in agent to "short check" it to there. If s/he asks why, you can say you have to get something from it - to swap papers to work with on the two flights, to give to a friend you're meeting at the airport, whatever. I doubt you'll get the third degree; while this isn't something two out of three passengers ask for, it's common enough not to raise eyebrows.