php根据经纬度算出公里数

<?php
/**
* Created by PhpStorm.
* User: Administrator
* Date: 2017/11/8
* Time: 13:06
*/

/**
* 根据起点坐标和终点坐标测距离
* @param  [array]   $from  [起点坐标(经纬度),例如:array(118.012951,36.810024)]
* @param  [array]   $to    [终点坐标(经纬度)]
* @param  [bool]    $km        是否以公里为单位 false:米 true:公里(千米)
* @param  [int]     $decimal   精度 保留小数位数
* @return [string]  距离数值
*/
function get_distance($from,$to,$km=true,$decimal=2){
sort($from);
sort($to);
$EARTH_RADIUS = 6370.996; // 地球半径系数

$distance = $EARTH_RADIUS*2*asin(sqrt(pow(sin( ($from[0]*pi()/180-$to[0]*pi()/180)/2),2)+cos($from[0]*pi()/180)*cos($to[0]*pi()/180)* pow(sin( ($from[1]*pi()/180-$to[1]*pi()/180)/2),2)))*1000;

if($km){
$distance = $distance / 1000;
}

return round($distance, $decimal);
}

$data=get_distance([116.359453,39.984363],[116.359806,39.983077]);
print_r($data);