<?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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