PHP计算两个经纬度之间的据离

/**
 * @param $lat1
 * @param $lng1
 * @param $lat2
 * @param $lng2
 * @return int
 */
function getDistance($lat1, $lng1, $lat2, $lng2){
 
    // 将角度转为狐度 
    $radLat1 = deg2rad($lat1);// deg2rad()函数将角度转换为弧度
    $radLat2 = deg2rad($lat2);
    $radLng1 = deg2rad($lng1);
    $radLng2 = deg2rad($lng2);
 
    $a = $radLat1 - $radLat2;
    $b = $radLng1 - $radLng2;
 
    $s = 2 * asin(sqrt(pow(sin($a / 2), 2)+cos($radLat1) * cos($radLat2) * pow(sin($b / 2), 2))) * 6378.137;
 
    return $s;
 
}
 
/**
 * @param $lat1
 * @param $lon1
 * @param $lat2
 * @param $lon2
 * @param float $radius  星球半径 KM
 * @return float
 */
function distance($lat1, $lon1, $lat2,$lon2,$radius = 6378.137)
{
    $rad = floatval(M_PI / 180.0);
 
    $lat1 = floatval($lat1) * $rad;
    $lon1 = floatval($lon1) * $rad;
    $lat2 = floatval($lat2) * $rad;
    $lon2 = floatval($lon2) * $rad;
 
    $theta = $lon2 - $lon1;
 
    $dist = acos(sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($theta));
 
    if ($dist < 0 ) {
        $dist += M_PI;
    }
    return $dist = $dist * $radius;
}
$lat1 = '31.253411';
$lon1 = '121.518998';
 
$lat2 = '31.277117';
$lon2 = '120.744587';
 
echo getDistance($lat1, $lon1, $lat2, $lon2);  // 73.734589823361
echo distance($lat1, $lon1, $lat2, $lon2);   // 73.734589823354