PHP PDO与MySQL的连接失败,mysql_connect工作正常

try {
    $dsn = "mysql:host=localhost;dbname=testdb";
    $username = "username";
    $password = "password";
    $pdo = new PDO($dsn, $username, $password);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

try {
    $dsn = "mysql:host=<您的数据库地址>;dbname=<您的数据库名>";
    $username = "<您的数据库用户名>";
    $password = "<您的数据库密码>";
    $pdo = new PDO($dsn, $username, $password);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}