这里是用的北京54坐标6度分带。需要用其他坐标可以修改参数$_a, $_f 。 经纬度转XY：
<?php
function BLtoXY($latitude, $longitude)
{
$_a = 6378245.0;
$_f = 1.0 / 298.3;
$zoneWide = 6;
$PI = 3.14159265353846;
$iPI = 0.0174532925199433; //3.1415926535898/180.0;
//ZoneWide = 6; //6度带宽
$ProjNo = floor($longitude / $zoneWide);
$longitude0 = $ProjNo * $zoneWide + $zoneWide / 2;
$longitude0 = $longitude0 * $iPI;
$latitude0 = 0;
$longitude1 = $longitude * $iPI; //经度转换为弧度
$latitude1 = $latitude * $iPI; //纬度转换为弧度
$e2 = 2 * $_f - $_f * $_f;
$ee = $e2 * (1.0 - $e2);
$NN = $_a / sqrt(1.0 - $e2 * sin($latitude1) * sin($latitude1));
$T = tan($latitude1) * tan($latitude1);
$C = $ee * cos($latitude1) * cos($latitude1);
$A = ($longitude1 - $longitude0) * cos($latitude1);
$M = $_a * ((1 - $e2 / 4 - 3 * $e2 * $e2 / 64 - 5 * $e2 * $e2 * $e2 / 256) * $latitude1 - (3 * $e2 / 8 + 3 * $e2 * $e2 / 32 + 45 * $e2 * $e2 * $e2 / 1024) * sin(2 * $latitude1) + (15 * $e2 * $e2 / 256 + 45 * $e2 * $e2 * $e2 / 1024) * sin(4 * $latitude1) - (35 * $e2 * $e2 * $e2 / 3072) * sin(6 * $latitude1));
$xval = $NN * ($A + (1 - $T + $C) * $A * $A * $A / 6 + (5 - 18 * $T + $T * $T + 72 * $C - 58 * $ee) * $A * $A * $A * $A * $A / 120);
$yval = $M + $NN * tan($latitude1) * ($A * $A / 2 + (5 - $T + 9 * $C + 4 * $C * $C) * $A * $A * $A * $A / 24 + (61 - 58 * $T + $T * $T + 600 * $C - 330 * $ee) * $A * $A * $A * $A * $A * $A / 720);
$X0 = 1000000 * ($ProjNo + 1) + 500000;
$Y0 = 0;
$X = round(($xval + $X0) * 100) / 100.0;
$Y = round(($yval + $Y0) * 100) / 100.0;
return array($X, $Y);
}
$lng = $_GET["lng"];
$lat = $_GET["lat"];
$XY = BLtoXY($lat, $lng);
echo json_encode($XY);
?>XY转经纬度：
<?php
function XYtoBL($X, $Y)
{
$_a = 6378245.0;
$_f = 1.0 / 298.3;
$zoneWide = 6;
$PI = 3.14159265353846;
$iPI = 0.0174532925199433; //3.1415926535898/180.0;
$ProjNo = floor($X / 1000000.0); //查找带号
$longitude0 = ($ProjNo - 1) * $zoneWide + $zoneWide / 2;
$longitude0 = $longitude0 * $iPI; //中央经线
$X0 = $ProjNo * 1000000 + 500000;
$Y0 = 0;
$xval = $X - $X0;
$yval = $Y - $Y0; //带内大地坐标
$e2 = 2 * $_f - $_f * $_f;
$e1 = (1.0 - sqrt(1 - $e2)) / (1.0 + sqrt(1 - $e2));
$ee = $e2 / (1 - $e2);
$M = $yval;
$u = $M / ($_a * (1 - $e2 / 4 - 3 * $e2 * $e2 / 64 - 5 * $e2 * $e2 * $e2 / 256));
$fai = $u + (3 * $e1 / 2 - 27 * $e1 * $e1 * $e1 / 32) * sin(2 * $u) + (21 * $e1 * $e1 / 16 - 55 * $e1 * $e1 * $e1 * $e1 / 32) * sin(4 * $u) + (151 * $e1 * $e1 * $e1 / 96) * sin(6 * $u) + (1097 * $e1 * $e1 * $e1 * $e1 / 512) * sin(8 * $u);
$C = $ee * cos($fai) * cos($fai);
$T = tan($fai) * tan($fai);
$NN = $_a / sqrt(1.0 - $e2 * sin($fai) * sin($fai));
$R = $_a * (1 - $e2) / sqrt((1 - $e2 * sin($fai) * sin($fai)) * (1 - $e2 * sin($fai) * sin($fai)) * (1 - $e2 * sin($fai) * sin($fai)));
$D = $xval / $NN;
//计算经度(Longitude) 纬度(Latitude)
$longitude1 = $longitude0 + ($D - (1 + 2 * $T + $C) * $D * $D * $D / 6 + (5 - 2 * $C + 28 * $T - 3 * $C * $C + 8 * $ee + 24 * $T * $T) * $D * $D * $D * $D * $D / 120) / cos($fai);
$latitude1 = $fai - ($NN * tan($fai) / $R) * ($D * $D / 2 - (5 + 3 * $T + 10 * $C - 4 * $C * $C - 9 * $ee) * $D * $D * $D * $D / 24 + (61 + 90 * $T + 298 * $C + 45 * $T * $T - 256 * $ee - 3 * $C * $C) * $D * $D * $D * $D * $D * $D / 720);
//转换为度 DD
$longitude = round(($longitude1 / $iPI) * 1000000) / 1000000.0;
$latitude = round(($latitude1 / $iPI) * 1000000) / 1000000.0;
return array($longitude, $latitude);
}
$X = $_GET["X"];
$Y = $_GET["Y"];
$latlng = XYtoBL($X, $Y);
echo json_encode($latlng);
?>