I’m not an expert, but I do remember that Philly and Pittsburgh are different than the rest of PA. Frepmail basil and maybe her Philly SAS folkls can speak to it.
As stated on this Pennsylvania Firearm Owners Association page, "It should be noted that permits issued by one county must be honored by all counties including Philadelphia regardless of rumors to the contrary." I am not a lawyer and this isn't legal advice, but I believe there was a major court decision that confirmed this.
HOWEVER, there are recently proposed attempts to overturn this--to allow Philadelphia to block concealed carry even with a valid Pennsylvania License To Carry Firearms (Concealed Carry Permit). Although I hope this doesn't go through, it's getting more likely as time goes on, I think. :-(