PHP PDO lastInsertId() function confusion

Question

I am confused with the way lastInsertId() function is written. Say for example I have the following queries with lastInsertId() function.

$myinsert = $pdo->prepare("INSERT INTO some_table(something)VALUE(:something");
$myinsert -> bindValue(':something', $something);
$myinsert -> execute();

$insert = $pdo->prepare("INSERT INTO table(something)VALUE(:something");
$insert-> bindValue(':something', $something);
$insert-> execute();
$lastId = $pdo->lastInsertId();

$stmt = $pdo->prepare("INSERT INTO another_table(something)VALUE(:something");
$stmt -> bindValue(':something', $something);
$stmt -> execute();

Now the confusion is that as everyone knows and can see here that in the satement $lastId = $pdo->lastInsertId(); there is no where mentioned whether to fetch the last inserted ID from $myinsert query or $insert query or from $stmt query. So how does it know where to fetch the ID from? Since, lastInsertId() function is placed above the $stmt query, it definitely will not fetch last inserted id from $stmt query as when the $lastid was declared $stmt query was not yet executed. But how does it know it has to fetch from $insert query and not from $myinsert query as in whole statement $lastId = $pdo->lastInsertId(); there is nothing defined like to fetch from so and so particular query? Please help me understand the way it works.

Answer 1

It will just give you the insert ID from the last insert prior to making the call which generates an auto-increment value. It could be that each insert will generate one, but it will only be the last one executed prior to this call.