Question: how to calculate distance between two zip codes in php?
Answer: R = earth's radius (mean radius = 6,371km) Δlat = lat2− lat1. Δlong = long2− long1. a = sin²(Δlat/2) + cos(lat1). cos(lat2). sin²(Δlong/2) c = 2. atan2(√a, √(1−a)) d = R.c.