PHP根据两点间的经纬度计算距离

/ 
 @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./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); 
}