Immigration you really have no control over, however it has got considerably better lately. More often than not people are waiting for their bags to arrive in the baggage hall. With regard to security, remember all the european flights into PHL arrive within a few hours of each other and many within minutes as they are invariably earlier than scheduled. In the event you clear customs along with 3 other plane loads who have just arrived then the security is indeed going to be a nightmare. My advice is to exit landside once you have rechecked your bags and clear security at term B C or D depending which one you are flying out from. BTW if you smoke you will welcome the walk outside as PHL is a total no smoking zone inside including the bars.