In Philadelphia, the most famous are various museums and historical sites. Among them, the Philadelphia Museum of Art, the City Hall and the Peace Bell in the downtown area are very famous. And around it (especially the Peace Bell), you can naturally buy all kinds of small souvenirs.
As for snacks, cheese sticks are a unique food that originated in Philadelphia, but they are inconvenient to carry. If the questioner is visiting Philadelphia, collecting coins and postcards is a cheap and unforgettable way.
Although Philadelphia has the earliest chewing gum (it is said) and ice cream shop in America ... but ... it tastes terrible!
In the market street, although not as good as new york, there are also large and small shops. If you want to buy luxury goods, you can also spend half a day shopping around. However, because it's only two and a half hours' drive from new york (ideally), you should go shopping in new york (laughs).
I hope it helps you. meow ...