this is probably too late to help, but you'll probably be fine. Even if you miss the flight, PHL-BOS is a high volume route and there are several more flights before the end of the day. Depending on how you are getting out of BOS, also consider PVD - providence is about an hour drive from boston, so you could change your pickup, or if desperate, take the train from PVD-South station Boston. Lots of options.

Good luck.