php类中如何连接mysql数据库表

<?php
    require_once('mysqli_driver.php');
?>

<?php
    require_once('pdo_driver.php');
?>

<?php
    $conn = mysqli_connect('localhost', 'username', 'password', 'database_name');
    if (!$conn) {
        die("Connection failed: " . mysqli_connect_error());
    }
?>

<?php
    $conn = new PDO('mysql:host=localhost;dbname=database_name', 'username', 'password');
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
?>

<?php
    $sql = "SELECT * FROM table_name";
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        while ($row = mysqli_fetch_assoc($result)) {
            echo "Column 1: " . $row["column1"] . " - Column 2: " . $row["column2"] . "<br>";
        }
    } else {
        echo "0 results";
    }
    mysqli_close($conn);
?>

<?php
    $sql = "SELECT * FROM table_name";
    $stmt = $conn->query($sql);
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    foreach ($result as $row) {
        echo "Column 1: " . $row["column1"] . " - Column 2: " . $row["column2"] . "<br>";
    }
?>