Php – Why there is a difference between PDO::lastInsertId and Mysql's LAST_INSERT_ID() behavior?

My current development environment is PHP 7.2.
This is MariaDB 10.3.11.

When using PDO’s lastInsertId function, if you run another query after the insert query, the lastInsertId result value will always be 0.

example table is

create table test
(
    id    int unsigned auto_increment comment 'PK' primary key,
    title varchar(128) charset utf8mb4 not null comment 'title'
)
comment 'test';

create table test2
(
    id    int unsigned auto_increment comment 'PK' primary key,
    title varchar(128) charset utf8mb4 not null comment 'title'
)
comment 'test2';

An example code is

public function pdoTest()
{
    $title = "test";
    $id = 1;

    $db = new PDO('mysql:host=<your-host>;port=<your-port>;dbname=<your-dbname>;charset=utf8', '<your-username>', '<your-password>');

    $db->beginTransaction();

    $query = "INSERT INTO test (title) VALUES (:title)";
    $stmt = $db->prepare($query);
    $stmt->bindParam(':title', $title);
    $stmt->execute();

    $updateQuery = "UPDATE test2 SET title = :title WHERE id = :id";
    $stmt = $db->prepare($updateQuery);
    $stmt->bindParam(':id', $id);
    $stmt->bindParam(':title', $title);
    $stmt->execute();

    echo $db->lastInsertId();
    $db->commit();
}

In the above situation, the return value of lastInsertId was 0. I searched the PHP site. Does anyone know why lastInsertId is not working properly?

I am wondering if only the insert query must be performed before executing the lastInsertId function.