根据两点间的经纬度计算距离

提供一个根据两点间的经纬度计算距离的方法

/**
 * 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.org/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 );
}