PHP calculates the distance between two points geographical coordinates

Function: Calculate the spherical distance between two points based on the pi ratio and the Earth radius coefficient and the longitude and latitude of the two point coordinates.
Get the coordinate distance of two points:

<code><span><span><?php </span><span>/**
 * 计算两点地理坐标之间的距离
 *<span> @param</span>  Decimal $longitude1 起点经度
 *<span> @param</span>  Decimal $latitude1  起点纬度
 *<span> @param</span>  Decimal $longitude2 终点经度 
 *<span> @param</span>  Decimal $latitude2  终点纬度
 *<span> @param</span>  Int     $unit       单位 1:米 2:公里
 *<span> @param</span>  Int     $decimal    精度 保留小数位数
 *<span> @return</span> Decimal
 */</span><span><span>function</span><span>getDistance</span><span>(<span>$longitude1</span>, <span>$latitude1</span>, <span>$longitude2</span>, <span>$latitude2</span>, <span>$unit</span>=<span>2</span>, <span>$decimal</span>=<span>2</span>)</span>{</span><span>$EARTH_RADIUS</span> = <span>6370.996</span>; <span>// 地球半径系数</span><span>$PI</span> = <span>3.1415926</span>;

    <span>$radLat1</span> = <span>$latitude1</span> * <span>$PI</span> / <span>180.0</span>;
    <span>$radLat2</span> = <span>$latitude2</span> * <span>$PI</span> / <span>180.0</span>;

    <span>$radLng1</span> = <span>$longitude1</span> * <span>$PI</span> / <span>180.0</span>;
    <span>$radLng2</span> = <span>$longitude2</span> * <span>$PI</span> /<span>180.0</span>;

    <span>$a</span> = <span>$radLat1</span> - <span>$radLat2</span>;
    <span>$b</span> = <span>$radLng1</span> - <span>$radLng2</span>;

    <span>$distance</span> = <span>2</span> * asin(sqrt(pow(sin(<span>$a</span>/<span>2</span>),<span>2</span>) + cos(<span>$radLat1</span>) * cos(<span>$radLat2</span>) * pow(sin(<span>$b</span>/<span>2</span>),<span>2</span>)));
    <span>$distance</span> = <span>$distance</span> * <span>$EARTH_RADIUS</span> * <span>1000</span>;

    <span>if</span>(<span>$unit</span>==<span>2</span>){
        <span>$distance</span> = <span>$distance</span> / <span>1000</span>;
    }

    <span>return</span> round(<span>$distance</span>, <span>$decimal</span>);

}

<span>// 起点坐标</span><span>$longitude1</span> = <span>113.330405</span>;
<span>$latitude1</span> = <span>23.147255</span>;

<span>// 终点坐标</span><span>$longitude2</span> = <span>113.314271</span>;
<span>$latitude2</span> = <span>23.1323</span>;

<span>$distance</span> = getDistance(<span>$longitude1</span>, <span>$latitude1</span>, <span>$longitude2</span>, <span>$latitude2</span>, <span>1</span>);
<span>echo</span><span>$distance</span>.<span>'m'</span>; <span>// 2342.38m</span><span>$distance</span> = getDistance(<span>$longitude1</span>, <span>$latitude1</span>, <span>$longitude2</span>, <span>$latitude2</span>, <span>2</span>);
<span>echo</span><span>$distance</span>.<span>'km'</span>; <span>// 2.34km</span><span>?></span></span></span></code>

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