I live in the Philly suburbs and work a mile from PHL. The Renaissance is a nice hotel as mentioned by the PP; you can probably get a good rate there. It is about a mile from PHL. I don't believe there is a charge for parking.
The Marriott is your best bet, but I would think it would be pricier considering the convenience. I am not sure how much they charge for parking.
There are a lot of options in the area. Some charge for parking and others do not. There is also a Comfort Inn and a Comfort Hotel a little further away, but still a quick trip to PHL. Both of them offer free breakfast at Denny's (next door to both) if my memory serves me correctly.