PHP编程：PHP根据两点间的经纬度计算距离

/** 
* @desc 依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); 
}