In Pennsylvania, you must have a permit to carry a handgun in a vehicle, whether openly or concealed, loaded or unloaded. For the purposes of carrying in a vehicle only--not for concealed carry outside a vehicle--Pennsylvania recognizes all otherstates' permits. However, to carry concealed outside a vehicle requires either a Pennsylvania permit or a permit from a state with which Pennsylvania has established reciprocity. In addition, you must have a Pennsylvania permit or a permit from a state with which Pennsylvania has established reciprocity to open carry within the city of Philadelphia.
Pennsylvania's reciprocity list is available at http://www.attorneygeneral.gov/crime.aspx?id=184