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;
}