如何在php中计算lat/long的距离？

function haversineDistance($lat1, $lon1, $lat2, $lon2) {
    $earthRadius = 6371; // 地球半径，单位为千米
    $lat1 = deg2rad($lat1);
    $lon1 = deg2rad($lon1);
    $lat2 = deg2rad($lat2);
    $lon2 = deg2rad($lon2);

    $latDiff = $lat2 - $lat1;
    $lonDiff = $lon2 - $lon1;

    $a = sin($latDiff / 2) * sin($latDiff / 2) +
         cos($lat1) * cos($lat2) *
         sin($lonDiff / 2) * sin($lonDiff / 2);
    $c = 2 * atan2(sqrt($a), sqrt(1 - $a));

    $distance = $earthRadius * $c;

    return $distance;
}

$lat1 = 39.9042;
$lon1 = 116.4074;
$lat2 = 23.0999;
$lon2 = 113.3245;

$distance = haversineDistance($lat1, $lon1, $lat2, $lon2);
echo "Distance between the two points: " . $distance . " km";