如何在PHP中打印连接的数据库信息(如db名称)？

$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名称";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "成功连接到数据库<br>";
} catch (PDOException $e) {
    echo "连接数据库失败: " . $e->getMessage();
}

echo "数据库名称: " . $conn->query("SELECT DATABASE()")->fetchColumn() . "<br>";

$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名称";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "成功连接到数据库<br>";
    echo "数据库名称: " . $conn->query("SELECT DATABASE()")->fetchColumn() . "<br>";
} catch (PDOException $e) {
    echo "连接数据库失败: " . $e->getMessage();
}