Dont use the crummy PHL lots. Many people use the parking lot by the Ramada for about $6/day plus about 10% tax. A couple of PHL airport hotels have some nice "stay and park" rates. These include Ramada (dreary hotel), Microtel (sometimes a really nice cheap deal, ie $69), Hampton Inn (newer and nicer) etc. Most are good for 7-14 nights parking, stay 1 night before or after you leave, and sometimes they will give you a couple of free extra days (call the hotel before you book).

MisterNice