如何使用CodeIgniter进行表格排序？

<?php
// Database connection
$db = new db();
$conn = $db->connect();
if (!$conn) {
    die("Connection failed: " . $db->error);
}

// Query
$query = "SELECT * FROM users ORDER BY first_name ASC, last_name DESC LIMIT 5";

// Execute query
$result = mysqli_query($conn, $query);

// Display data
echo<table border=1>
      <tr>
       <th>First Name</th>
       <th>Last Name</th>
       <th>Email</th>
      </tr>";

if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        echo "<tr>
             <td>" . $row["first_name"] . "</td>
             <td>" . $row["last_name"] . "</td>
             <td>" . $row["email"] . "</td>
           </tr>";
        }
    } else {
        echo "<tr><td colspan=3>No rows found</td></tr>";
    }
    echo "</table>";
?>