仅显示用户选择范围内的结果

Question

我有一个存储经纬度坐标的数据库表。用户输入他们的邮政编码并应选择一个范围，例如 5 英里，然后应显示数据库中存储的 5 英里范围内的所有坐标。我已设法将用户输入的邮政编码转换为坐标，但我发现很难在下一部分中仅显示所选英里范围内的结果。

<?php
$postcode = urlencode("$_POST[postcode]"); // post code to look up in this case status however can easily be retrieved from a database or a form post
$request_url = "http://maps.googleapis.com/maps/api/geocode/xml?address=".$postcode."&sensor=true"; // the request URL you'll send to google to get back your XML feed
$xml = simplexml_load_file($request_url) or die("url not loading");// XML request
$status = $xml->status;// GET the request status as google's api can return several responses
if ($status=="OK") {
    //request returned completed time to get lat / lang for storage
    $lat = $xml->result->geometry->location->lat;
    $long = $xml->result->geometry->location->lng;

}
echo "$lat,$long";

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}


$sql = "SELECT * FROM location";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
// output data of each row
while($row = mysqli_fetch_assoc($result)) {
    echo " Hobby: " . $row["lat"]. " Location: " . $row["long"]. "<br>";
    $lat1=$row["lat"];
    echo $lat1;
}
} else {
echo "Sorry, there are no meetups yet you can create one here ";
}

mysqli_close($conn);

     ?>

Answer 1

如果您有一个 mySQL 数据库，请查看这些问题，它们处理相同的问题。

Mysql within distance query

https://gis.stackexchange.com/questions/31628/find-points-within-a-distance-using-mysql

您需要创建一个 SQL 语句，其中一定距离内的所有坐标都是结果。它可能看起来像：

SELECT *, 
   ( 3959 * acos( cos( radians($lat) ) 
   * cos( radians( lat ) ) 
   * cos( radians( lng ) - radians($lng) ) 
   + sin( radians($lat) ) 
   * sin( radians( lat ) ) ) ) AS distance 
FROM locations 
HAVING distance < $miles 
ORDER BY distance 
LIMIT 0, 20

如果您有 postgres 数据库，则可以使用 postGIS 扩展。存在一个函数 ST_DWithin，如果坐标在一定距离内，则返回 true。