A cheesesteak sandwich exists every except in Philadelphia, where it just called a steak sandwich or hoagie. Go there and ask for a Philly cheesesteak sandwich on a roll and you will be immediately be recognized as an outsider or a hated tourist.
Order it any way other than with provolone, white cheddar or Cheez Whiz and you will be mocked by all present all the way back to the airport. Those insisting that the thinly sliced meat be nicely laid out in the roll in the thin sheets it comes in instead of scrambled on the grill might have themselves scrambled on the grill. Such is the harsh reality of fine dining in Philadelphia.