Example sharing of distance calculation in PHP Baidu map development

Baidu map interface will be used in many project development, so how to calculate the distance between two coordinates is also a typical application developed for Baidu map interface. This article shares an example of distance calculation in Baidu map development to help everyone become familiar with the development of Baidu map.

The specific implementation method is as follows:

/**
 * 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;
}

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