如何使用php函数来优化分页展示和排序功能？

<?php
// 数据库连接
$conn = mysqli_connect("localhost", "username", "password", "database");

// 每页显示的数据数量
$limit = 10;

// 查询总数据量
$totalQuery = "SELECT COUNT(*) as total FROM table";
$totalResult = mysqli_query($conn, $totalQuery);
$totalData = mysqli_fetch_assoc($totalResult)['total'];

// 计算总页数
$totalPages = ceil($totalData / $limit);

// 当前页码
$page = isset($_GET['page']) ? $_GET['page'] : 1;

// 设置起始位置
$start = ($page - 1) * $limit;

// 查询当前页的数据
$query = "SELECT * FROM table LIMIT $start, $limit";
$result = mysqli_query($conn, $query);

// 展示数据
while ($row = mysqli_fetch_assoc($result)) {
    // 数据展示代码
}

// 分页导航
for ($i = 1; $i <= $totalPages; $i++) {
    if ($i == $page) {
        echo "<span>$i</span>";
    } else {
        echo "<a href='page.php?page=$i'>$i</a>";
    }
}

// 关闭数据库连接
mysqli_close($conn);
?>

<?php
// 数据库连接
$conn = mysqli_connect("localhost", "username", "password", "database");

// 排序字段和排序方式
$orderBy = isset($_GET['orderby']) ? $_GET['orderby'] : 'id';
$order = isset($_GET['order']) ? $_GET['order'] : 'ASC';

// 查询数据并排序
$query = "SELECT * FROM table ORDER BY $orderBy $order";
$result = mysqli_query($conn, $query);

// 展示数据
while ($row = mysqli_fetch_assoc($result)) {
    // 数据展示代码
}

// 排序链接
echo "<a href='page.php?orderby=id&order=ASC'>ID ASC</a>";
echo "<a href='page.php?orderby=id&order=DESC'>ID DESC</a>";

// 关闭数据库连接
mysqli_close($conn);
?>