php如何计算两坐标点之间的距离

//两点间距离比较近
function getDistance($lat1, $lng1, $lat2, $lng2) 
{ 
 $earthRadius = 6367000; //地球半径m

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

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

 $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); 
} 

//两点间距离比较远
function getLongDistance($lat1, $lng1, $lat2,$lng2,$radius = 6378.137)
{
 $rad = floatval(M_PI / 180.0);

 $lat1 = floatval($lat1) * $rad;
 $lng1 = floatval($lng1) * $rad;
 $lat2 = floatval($lat2) * $rad;
 $lng2 = floatval($lng2) * $rad;

 $theta = $lng2 - $lng1;

 $dist = acos(sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($theta));

 if ($dist  0 ) {
  $dist += M_PI;
 }
 return $dist = $dist * $radius;
}

 ?php 
 define('EARTH_RADIUS', 6378.137);//地球半径 
 define('PI', 3.1415926); 
 /** 
 * 计算两组经纬度坐标 之间的距离 
 * params ：lat1 纬度1； lng1 经度1； lat2 纬度2； lng2 经度2； len_type （1:m or 2:km); 
 * return m or km 
 */ 
 function GetDistance($lat1, $lng1, $lat2, $lng2, $len_type = 1, $decimal = 2) 
 { 
 $radLat1 = $lat1 * PI / 180.0; 
 $radLat2 = $lat2 * PI / 180.0; 
 $a = $radLat1 - $radLat2; 
 $b = ($lng1 * PI / 180.0) - ($lng2 * PI / 180.0); 
 $s = 2 * asin(sqrt(pow(sin($a/2),2) + cos($radLat1) * cos($radLat2) * pow(sin($b/2),2))); 
 $s = $s * EARTH_RADIUS; 
 $s = round($s * 1000); 
 if ($len_type > 1) 
 { 
 $s /= 1000; 
 } 
 return round($s, $decimal); 
 } 
 echo GetDistance(39.908156,116.4767, 39.908452,116.450479, 1);//输出距离/米