# Calculate Distance Between Two ZIP Codes or Postal Codes

By Hexa SDC
on July 24, 2004

Version: 1.0

Type: Function

Category: Algorithms

Description: This algorithm calculates distance between two coordinates ie. latitude and longitude from ZIP code or postal code. It is suitable for store locator, route planner, shipment estimation etc.

```<?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                                  :*/
/*::  United States zip code and Canadian postal code databases with latitude & :*/
/*::  longitude are available at http://www.zipcodeworld.com                 :*/
/*::                                                                         :*/
/*::                                                                         :*/
/*::  Official web site: http://www.zipcodeworld.com                         :*/
/*::                                                                         :*/
/*::                                                                         :*/
/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
function distance(\$lat1, \$lon1, \$lat2, \$lon2, \$unit) {

\$theta = \$lon1 - \$lon2;
\$dist = acos(\$dist);
\$miles = \$dist * 60 * 1.1515;
\$unit = strtoupper(\$unit);

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

echo distance(32.9697, -96.80322, 29.46786, -98.53506, "m") . " miles<br>";
echo distance(32.9697, -96.80322, 29.46786, -98.53506, "k") . " kilometers<br>";
echo distance(32.9697, -96.80322, 29.46786, -98.53506, "n") . " nautical miles<br>";

?>

```
﻿