mysql_connect未定义

<?php
$host = 'localhost';
$user = 'username';
$password = 'password';
$dbname = 'database_name';

// 创建连接
$conn = mysqli_connect($host, $user, $password, $dbname);

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

echo 'Connected successfully';

// 关闭连接
mysqli_close($conn);
?>

<?php
$host = 'localhost';
$dbname = 'database_name';
$user = 'username';
$password = 'password';

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname;charset=utf8", $user, $password);
    // 设置 PDO 错误模式为异常
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo 'Connected successfully';
} catch(PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}
?>