php怎么访问数据库

$host = 'localhost';
$user = 'username';
$password = 'password';
$dbname = 'database_name';

$conn = mysqli_connect($host, $user, $password, $dbname);

if (!$conn) {
    die('Connection failed: ' . mysqli_connect_error());
}

$sql = "SELECT id, name FROM users";
$result = mysqli_query($conn, $sql);

while ($row = mysqli_fetch_assoc($result)) {
    echo 'ID: ' . $row['id'] . ' - Name: ' . $row['name'] . '<br>';
}

mysqli_close($conn);

$host = 'localhost';
$dbname = 'database_name';
$user = 'username';
$password = 'password';

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname;charset=utf8", $user, $password);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $sql = "SELECT id, name FROM users";
    $stmt = $pdo->query($sql);

    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo 'ID: '': $row['id'] . ' - Name: ' . $row['name'] . '<br>';
    }
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}

$pdo = null;