PHP uses the longitude and latitude between two points to calculate the straight-line distance between two points

    /**
     *  计算两组经纬度坐标 之间的距离
     *   params ：lat1 纬度1； lng1 经度1； lat2 纬度2； lng2 经度2； len_type （1:m or 2:km);
     *   return m or km
     */
	 
     function GetDistance($lat1, $lng1, $lat2, $lng2, $len_type = 1, $decimal = 2)
    {
       $radLat1 = $lat1 * PI ()/ 180.0;   //PI()圆周率
       $radLat2 = $lat2 * PI() / 180.0;
       $a = $radLat1 - $radLat2;
       $b = ($lng1 * PI() / 180.0) - ($lng2 * PI() / 180.0);
       $s = 2 * asin(sqrt(pow(sin($a/2),2) + cos($radLat1) * cos($radLat2) * pow(sin($b/2),2)));
       $s = $s * 6378.137;
       $s = round($s * 1000);
       if ($len_type --> 1)
       {
           $s /= 1000;
       }
   return round($s, $decimal);
	}
	$Xian = array(
			'lat'=>'34.2620480000',
			'lng'=>'108.9408590000'
			);
	$Chengdu = array(
			'lat'=>'30.6736560000',
			'lng'=>'104.0107450000'
			);
	echo '西安距成都'.GetDistance($Xian['lat'],$Xian['lng'],$Chengdu['lat'],$Chengdu['lng'],2).'km';