Sealed Philadelphia cream cheese left out overnight, is it still safe to eat?
Probably, but depends on brand. More precisely, on manufacturing and packaging processes. If it was subject to some equivalent of pasteurization and is still sealed, probability it spoiled is minimal. If it contains preservatives, it helps. Some brands also have citric acid, and low pH helps to make them a bit shelf stable. 

If seal is broken, or if it wasn't pasteurized (or something like that) and does not contain any preservatives, discard it. Otherwise, if it looks good, smells good and tastes good, I'd guess it to be all right, but there is a high chance what I ate was different from your cheese, so no promises. And don't give it to eldry, pregnant or children. You know, better safe than sorry.