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

It can be done with just maths...

function calc_distance($point1, $point2)
{
    $distance = (3958 * 3.1415926 * sqrt(
            ($point1['lat'] - $point2['lat'])
            * ($point1['lat'] - $point2['lat'])
            + cos($point1['lat'] / 57.29578)
            * cos($point2['lat'] / 57.29578)
            * ($point1['long'] - $point2['long'])
            * ($point1['long'] - $point2['long'])
        ) / 180);

    return $distance;
}