If you're looking for a meeting place or a good stop around ½ or halfway between Philadelphia and Hartford, you can try Yonkers, NY, which is about 2 hours northeast of Philadelphia, or almost 2 hours southwest of Hartford.
About ¼ or a fourth of the way, you can stop at Edison, NJ. This is almost an hour northeast of Philadelphia.
About ⅓ or a third of the way, you can stop at Newark, NJ. This is a little over 1 hour northeast of Philadelphia.
If you drive straight through without stopping at all, the total distance is 211 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 3 hours, 35 minutes.