PHP计算两个经纬度之间的距离

/**
*  @desc 根据两点间的经纬度计算距离
*  @param float $lat 纬度值
*  @param float $lng 经度值
*/
function getDistance($lat1, $lng1, $lat2, $lng2)
{
$earthRadius = 6367000; //approximate radius of earth in meters

/*
Convert these degrees to radians
to work with the formula
*/

$lat1 = ($lat1 * pi() ) / 180;
$lng1 = ($lng1 * pi() ) / 180;

$lat2 = ($lat2 * pi() ) / 180;
$lng2 = ($lng2 * pi() ) / 180;

/*
Using the
Haversine formula
 http://en.wikipedia.org/wiki/Haversine_formula 
calculate the distance
*/

$calcLongitude = $lng2 - $lng1;
$calcLatitude = $lat2 - $lat1;
$stepOne = pow(sin($calcLatitude / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($calcLongitude / 2), 2);
$stepTwo = 2 * asin(min(1, sqrt($stepOne)));
$calculatedDistance = $earthRadius * $stepTwo;

return round($calculatedDistance);
}