Calculating distance using latitude and longitude

calc-lat-lng-php.php

<?php

// http://www.movable-type.co.uk/scripts/latlong.html
// converted from JS to PHP
$d_lat = deg2rad($lat1 - $lat2);
$d_lon = deg2rad($lon1 - $lon2);

$lat1 = deg2rad($lat1);
$lat2 = deg2rad($lat2);

$r = 6371; // km
$a = sin($d_lat / 2) * sin($d_lat / 2) +
     sin($d_lon / 2) * sin($d_lon / 2) *
     cos($lat1) * cos($lat2);
$c = 2 * atan2(sqrt($a), sqrt(1 - $a));
$d = $r * $c;

calc-lat-lng-sql.php

<?php
/**
 * function to create the sql for finding the distance between 2 lat/lng pairs
 */
//$unit = '6367.45'; 
//$unit = '3978';
function distance($lat_from, $lng_from, $lat_to, $lng_to, $unit = '3978') { 
     return ‘ROUND($unit * acos(sin(‘.$lat_from.’) * sin(‘.$lat_to.’) + cos(‘.$lat_from.’) * cos(‘.$lat_to.’) * cos(‘.$lng_from.’ - ‘.$lng_to.’)))’; 
}

//Use it like this:
$latitude = '40.7397960';
$longitude = '-73.9979390';

$sql = "SELECT ".distance(deg2rad($latitude), deg2rad($longitude), deg2rad(`s`.`lat_rad`), deg2rad(`s`.`lng_rad`))." AS `distance` FROM `sometable` AS `s` WHERE ".distance(deg2rad($latitude), deg2rad($longitude), deg2rad(`s`.`lat_rad`), deg2rad(`s`.`lng_rad`))." < '".$max_distance."'";