Location: PHPKode > scripts > Geocoder > geocoder/MathUtils.inc
<?php

/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*::                                                                         :*/
/*::  this routine calculates the distance between two points (given the     :*/
/*::  latitude/longitude of those points). it is being used to calculate     :*/
/*::  the distance between two zip codes or postal codes using our           :*/
/*::  zipcodeworld(tm) and postalcodeworld(tm) products.                     :*/
/*::                                                                         :*/
/*::  definitions:                                                           :*/
/*::    south latitudes are negative, east longitudes are positive           :*/
/*::                                                                         :*/
/*::  passed to function:                                                    :*/
/*::    lat1, lon1 = latitude and longitude of point 1 (in decimal degrees)  :*/
/*::    lat2, lon2 = latitude and longitude of point 2 (in decimal degrees)  :*/
/*::    unit = the unit you desire for results                               :*/
/*::           where: 'm' is statute miles                                   :*/
/*::                  'k' is kilometers (default)                            :*/
/*::                  'n' is nautical miles                                  :*/
/*::                                                                         :*/
/*::   see http://www.zipcodeworld.com/samples/distance.php.html             :*/
/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/


function distance($lat1, $lon1, $lat2, $lon2, $unit) {

    $theta = $lon1 - $lon2;
    $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) +  cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
    $dist = acos($dist);
    $dist = rad2deg($dist);
    $miles = $dist * 60 * 1.1515;
    $unit = strtoupper($unit[0]);

    if ($unit == "K") {
        return ($miles * 1.609344);
    }
    else if ($unit == "N") {
        return ($miles * 0.8684);
    }
    else {
        return $miles;
    }
}


?>
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