php计算2点的经纬度距离

/**
*  @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./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);
 }