如何在php中统计同城用户

<?php
// 获取用户的地理位置信息（示例使用固定的经纬度坐标）
$userLatitude = 39.9042;
$userLongitude = 116.4074;

// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查数据库连接是否成功
if ($conn->connect_error) {
    die("数据库连接失败: " . $conn->connect_error);
}

// 查询同城用户
$sql = "SELECT COUNT(*) AS total FROM users WHERE ABS(latitude - $userLatitude) < 0.1 AND ABS(longitude - $userLongitude) < 0.1";
$result = $conn->query($sql);

// 检查查询结果
if ($result->num_rows > 0) {
    // 输出同城用户数量
    $row = $result->fetch_assoc();
    echo "同城用户数量: " . $row["total"];
} else {
    echo "没有找到同城用户";
}

// 关闭数据库连接
$conn->close();
?>