Calculating distance between zip codes in PHP

Question

I grabbed a database of the zip codes and their langitudes/latitudes, etc from this This page. It has got the following fields:

ZIP, LATITUDE, LONGIT

Answer 1

Check out the Haversine formula for calculating great circle distances between two points. Some more samples can be found here

Haversine formula:

• 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

(Note that angles need to be in radians to pass to trig functions).