/**
 * [GetDistance 计算两个进纬度之间的距离]
 * @param [float] $lat1 [纬度1]
 * @param [float] $lng1 [经度1]
 * @param [float] $lat2 [纬度2]
 * @param [float] $lng2 [经度2]
 * @return[float]       [两个坐标距离值]
 */
function GetDistance($lat1, $lng1, $lat2, $lng2)
{
    $pi = 3.1415926535898;
    $earth_radius = 6378.137;

    $radLat1 = $lat1 * ($pi / 180);
    $radLat2 = $lat2 * ($pi / 180);

    $a = $radLat1 - $radLat2; 
    $b = ($lng1 * ($pi / 180)) - ($lng2 * ($pi / 180)); 

    $s = 2 * asin(sqrt(pow(sin($a/2),2) + cos($radLat1)*cos($radLat2)*pow(sin($b/2),2))); 
    $s = $s * $earth_radius; 
    $s = round($s * 10000) / 10000; 
    return $s; 
}