根据经纬度判断位置

<?php
/**

• @desc 根据两点间的经纬度计算距离
• @param float $lat 纬度值
• @param float $lng 经度值

*/
function getDistance($lat1, $lng1, $lat2, $lng2){

$earthRadius = 6367000; //approximate radius of earth in meters
$lat1 = ($lat1 * pi() ) / 180;
$lng1 = ($lng1 * pi() ) / 180;
$lat2 = ($lat2 * pi() ) / 180;
$lng2 = ($lng2 * pi() ) / 180;
$calcLongitude = $lng2 - $lng1;
$calcLatitude = $lat2 - $lat1;
$stepOne = pow(sin($calcLatitude / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($calcLongitude / 2), 2);
$stepTwo = 2 * asin(min(1, sqrt($stepOne)));
$calculatedDistance = $earthRadius * $stepTwo;
// return round($calculatedDistance);
return $calculatedDistance;

}

// 循环调用然后依次返回距离
/**
* 计算某个经纬度的周围某段距离的正方形的四个点
*
*@param lng float 经度
*@param lat float 纬度
*@param distance float 该点所在圆的半径，该圆与此正方形内切，默认值为 5 千米
*@return array 正方形的四个点的经纬度坐标
*/
function returnSquarePoint($lng, $lat,$distance = 5)
{

$dlng =  2 * asin(sin($distance / (2 * 6371)) / cos(deg2rad($lat)));
$dlng = rad2deg($dlng);

$dlat = $distance/6371;// 地球半径，平均半径为 6371km
$dlat = rad2deg($dlat);
return array('left-top'=>array('lat'=>$lat + $dlat,'lng'=>$lng-$dlng),
    'right-top'=>array('lat'=>$lat + $dlat, 'lng'=>$lng + $dlng),
    'left-bottom'=>array('lat'=>$lat - $dlat, 'lng'=>$lng - $dlng),
    'right-bottom'=>array('lat'=>$lat - $dlat, 'lng'=>$lng + $dlng)
);

}

// 计算附近五公里的经纬度范围
// 根据这个范围到数据库查询满足条件的店面
/**

• 获取一定范围内的地点

*/
function getSiteData($lng,$lat,$userType)
{

// 使用此函数计算得到结果后，带入 sql 查询。$squares = $this->returnSquarePoint($lng, $lat);

if($squares['left-top']['lng'] > $squares['right-bottom']['lng']){$lngMin = $squares['right-bottom']['lng'];
    $lngMax = $squares['left-top']['lng'];
}else{$lngMin = $squares['left-bottom']['lng'];
    $lngMax = $squares['right-top']['lng'];
}

if($squares['left-top']['lat'] > $squares['right-bottom']['lat']){$latMin = $squares['right-bottom']['lat'];
    $latMax = $squares['left-top']['lat'];
}else{$latMin = $squares['left-top']['lat'];
    $latMax = $squares['right-bottom']['lat'];
}
$where = "lng<>0 and lng>=$lngMin and lng<=$lngMax and lat>=$latMin and lat<=$latMax and status=1";
if($userType){$where .= "AND type = 2";}else{$where .= "AND type = 1";}
$site_info = M('Site')->field('id,address,lat,lng')->where($where)->select();

return $site_info;

}