# 兩點座標的直線距離

```php
    /**
     * 計畫兩個座標的直線距離
     * @param  [string] $lng1 [使用者所在位置經度]
     * @param  [string] $lat1 [使用者所在位置緯度]
     * @param  [string] $lng2 [附近店家經度]
     * @param  [string] $lat2 [附近店家緯度]
     * @return [string]       [兩點距離]
     */
    function getdistance($lng1,$lat1,$lng2,$lat2){
        //將角度轉換為弧度
        $radLat1=deg2rad($lat1);
        $radLat2=deg2rad($lat2);
        $radLng1=deg2rad($lng1);
        $radLng2=deg2rad($lng2);
        $a=$radLat1-$radLat2;
        $b=$radLng1-$radLng2;
        $s=2*asin(sqrt(pow(sin($a/2),2)+cos($radLat1)*cos($radLat2)*pow(sin($b/2),2)))*6378.137;//6378.137為地球的半徑
        return $s;
    }
```


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