按从数组计算的值对数组进行排序

Question

我有一个数组中来自数据库的用户的 lat 和 lng 我有我的纬度和经度

现在我想计算距离并用它对数据库中的用户进行排序

$mylat = $_SESSION['lat'];
$mylng = $_SESSION['lng'];

$statement = $pdo->prepare("SELECT * FROM users");
$statement->execute();
$users = $statement->fetchAll();

foreach($users as $row){
    $dist = 0.0;
    $x1 = $mylng;
    $x2 = $row['lng'];
    $y1 = $mylat;
    $y2 = $row['lat'];

    $dist = acos(sin($x1=deg2rad($x1))*sin($x2=deg2rad($x2))+cos($x1)*cos($x2)*cos(deg2rad($y2) - deg2rad($y1)))*(6378.137);
    $distn = FLOOR ( ROUND($dist,1) * 2 ) / 2 ;
}

sort($distn);

foreach ($users as $row) { 

$dist = 0.0;
    $x1 = $mylng;
    $x2 = $row['lng'];
    $y1 = $mylat;
    $y2 = $row['lat'];

    $dist = acos(sin($x1=deg2rad($x1))*sin($x2=deg2rad($x2))+cos($x1)*cos($x2)*cos(deg2rad($y2) - deg2rad($y1)))*(6378.137);
    $distn = FLOOR ( ROUND($dist,1) * 2 ) / 2 ;

echo $row['username'];
echo $distn;

}

所以在第一个 foreach 中，我计算了每个用户到我的距离。 比我想在与我的距离之后对用户进行排序并显示它们 有名字，离我有距离。

user1 0.5km distance
user2 1km distance

但我不会工作。 谢谢你的帮助:)

Answer 1

创建距离函数：

function getDistance ($lat, $lon)
{
    global $mylng, $mylat;
    $x1 = deg2rad($mylng);
    $x2 = deg2rad($lon);
    $y1 = deg2rad($mylat);
    $y2 = deg2rad($lat);

    $dist = acos(sin($x1)*sin($x2)+cos($x1)*cos($x2)*cos($y2 - $y1))*(6378.137);
    return $dist;
}

创建比较函数：

function compareDistance ($user1, $user2)
{
    return getDistance ($user1['lat'], $user1['lng']) - getDistance ($user2['lat'], $user2['lng']);
}

然后你可以通过uasort传递你的数组：

uasort ($users, 'compareDistance');

更多信息请参见http://php.net/manual/en/function.uasort.php。

编辑：

你的程序可以重写：

function getDistance ($lat, $lon)
{
    global $mylng, $mylat;

    $x1 = deg2rad($mylng);
    $x2 = deg2rad($lon);
    $y1 = deg2rad($mylat);
    $y2 = deg2rad($lat);

    $dist = acos(sin($x1)*sin($x2)+cos($x1)*cos($x2)*cos($y2 - $y1))*(6378.137);
    return $dist;
}

function compareDistance ($user1, $user2)
{
    return getDistance ($user1['lat'], $user1['lng']) - getDistance ($user2['lat'], $user2['lng']);
}

$mylat = $_SESSION['lat'];
$mylng = $_SESSION['lng'];

$statement = $pdo->prepare("SELECT * FROM users");
$statement->execute();
$users = $statement->fetchAll();

uasort ($users, 'compareDistance');

foreach ($users as $row) { 
    $dist = getDistance ($row['lat'], $row['lng']);
    $distn = floor(round($dist,1) * 2) / 2 ;

    echo $row['username']. ": " . $distn . "km distance";
}