php捕捉mysql错误

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 执行查询
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if (!$result) {
    echo "查询失败: " . $conn->error;
} else {
    // 输出结果
    while($row = $result->fetch_assoc()) {
        echo $row["firstname"] . " " . $row["lastname"] . "<br>";
    }
}

$conn->close();
?>

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // 设置PDO错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $sql = "SELECT id, firstname, lastname FROM MyGuests";
    $result = $conn->query($sql);

    // 设置结果集为关联数组
    $result->setFetchMode(PDO::FETCH_ASSOC);
    foreach($result as $row) {
        echo $row["firstname"] . " " . $row["lastname"] . "<br>";
    }
} catch(PDOException $e) {
    echo "数据库连接失败: " . $e->getMessage();
}

$conn = null;
?>