PHP realizes the function of searching nearby people

First of all, we should think like this: Now that we know the longitude and latitude of the user's current location and the range we are going to search, can we calculate a range? That is to say, based on a center point and radius, calculate the maximum and minimum values ​​of longitude and latitude that meet the conditions.

Detailed implementation:

So here, friends who want to think independently and complete it, don’t continue reading.
We mentioned an implementation principle of this function above, and then we will explain the specific implementation steps.
We first declare a function to calculate the range of latitude and longitude:

##

/**
 * 根据经纬度和半径计算出范围
 * @param string $lat 纬度
 * @param String $lng 经度
 * @param float $radius 半径
 * @return Array 范围数组
 */
private function calcScope($lat, $lng, $radius) {
  $degree = (24901*1609)/360.0;
  $dpmLat = 1/$degree;

  $radiusLat = $dpmLat*$radius;
  $minLat = $lat - $radiusLat;    // 最小纬度
  $maxLat = $lat + $radiusLat;    // 最大纬度

  $mpdLng = $degree*cos($lat * (PI/180));
  $dpmLng = 1 / $mpdLng;
  $radiusLng = $dpmLng*$radius;
  $minLng = $lng - $radiusLng;   // 最小经度
  $maxLng = $lng + $radiusLng;   // 最大经度

  /** 返回范围数组 */
  $scope = array(
    'minLat'  => $minLat,
    'maxLat'  => $maxLat,
    'minLng'  => $minLng,
    'maxLng'  => $maxLng
    );
  return $scope;
}

The returned array contains the conditions within the $radius range. Maximum and minimum latitude and longitude.

Now that we have obtained the range, we can start to search from the database for all records that meet the conditions within this latitude and longitude range:

/**
 * 根据经纬度和半径查询在此范围内的所有的电站
 * @param String $lat  纬度
 * @param String $lng  经度
 * @param float $radius 半径
 * @return Array     计算出来的结果
 */
public function searchByLatAndLng($lat, $lng, $radius) {
  $scope = $this->calcScope($lat, $lng, $radius);   // 调用范围计算函数，获取最大最小经纬度
  /** 查询经纬度在 $radius 范围内的电站的详细地址 */
  $sql = &#39;SELECT `字段` FROM `表名` WHERE `Latitude` < &#39;.$scope[&#39;maxLat&#39;].&#39; and `Latitude` > &#39;.$scope[&#39;minLat&#39;].&#39; and `Longitude` < &#39;.$scope[&#39;maxLng&#39;].&#39; and `Longitude` > &#39;.$scope[&#39;minLng&#39;];

  $stmt = self::$db->query($sql);
  $res = $stmt->fetchAll(PDO::FETCH_ASSOC);    // 获取查询结果并返回
  return $res;
}

Extension:

Until now, we have known how to calculate nearby people, but in actual needs, we often need to calculate the actual distance between each person and the current center point distance.

Next, let’s look at another method:

/**
 * 获取两个经纬度之间的距离
 * @param string $lat1 纬一
 * @param String $lng1 经一
 * @param String $lat2 纬二
 * @param String $lng2 经二
 * @return float 返回两点之间的距离
 */
public function calcDistance($lat1, $lng1, $lat2, $lng2) {
  /** 转换数据类型为 double */
  $lat1 = doubleval($lat1);
  $lng1 = doubleval($lng1);
  $lat2 = doubleval($lat2);
  $lng2 = doubleval($lng2);
  /** 以下算法是 Google 出来的，与大多数经纬度计算工具结果一致 */
  $theta = $lng1 - $lng2;
  $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
  $dist = acos($dist);
  $dist = rad2deg($dist);
  $miles = $dist * 60 * 1.1515;
  return ($miles * 1.609344);
}

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PHP Query nearby people And how to implement distance, PHP query distance implementation_PHP tutorial

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