PHP计算百度地图两个GPS坐标之间距离的方法

/**

 * 计算两个坐标之间的距离(米)

 * @param float $fP1Lat 起点(纬度)

 * @param float $fP1Lon 起点(经度)

 * @param float $fP2Lat 终点(纬度)

 * @param float $fP2Lon 终点(经度)

 * @return int

 */

function distanceBetween($fP1Lat, $fP1Lon, $fP2Lat, $fP2Lon){

    $fEARTH_RADIUS = 6378137;

    //角度换算成弧度

    $fRadLon1 = deg2rad($fP1Lon);

    $fRadLon2 = deg2rad($fP2Lon);

    $fRadLat1 = deg2rad($fP1Lat);

    $fRadLat2 = deg2rad($fP2Lat);

    //计算经纬度的差值

    $fD1 = abs($fRadLat1 - $fRadLat2);

    $fD2 = abs($fRadLon1 - $fRadLon2);

    //距离计算

    $fP = pow(sin($fD1/2), 2) +

          cos($fRadLat1) * cos($fRadLat2) * pow(sin($fD2/2), 2);

    return intval($fEARTH_RADIUS * 2 * asin(sqrt($fP)) + 0.5);

}

/**

 * 百度坐标系转换成标准GPS坐系

 * @param float $lnglat 坐标(如:106.426, 29.553404)

 * @return string 转换后的标准GPS值:

 */

function BD09LLtoWGS84($fLng, $fLat){ // 经度,纬度

    $lnglat = explode(',', $lnglat);

    list($x,$y) = $lnglat;

    $Baidu_Server = "http://api.map.baidu.com/ag/coord/convert?from=0&to=4&x={$x}&y={$y}";

    $result = @file_get_contents($Baidu_Server);

    $json = json_decode($result);

    if($json->error == 0){

        $bx = base64_decode($json->x);

        $by = base64_decode($json->y);

        $GPS_x = 2 * $x - $bx;

        $GPS_y = 2 * $y - $by;

        return $GPS_x.','.$GPS_y;//经度,纬度

    }else

        return $lnglat;

}