Get last insert id after a prepared insert with PDO

I'm using PHP PDO with PostgreSQL for a new project.

Given the following function, how can I return the id of the row just inserted? It doesn't work the way it looks now.

function adauga_administrator($detalii) {
    global $db;
    $ultima_logare = date('Y-m-d');

    $stmt = $db->prepare("INSERT INTO site_admins (sa_nume, sa_prenume, sa_user_name, sa_p开发者_开发问答assword, sa_email, sa_id_rol, sa_status, sa_ultima_logare) VALUES (?, ?, ?, ?, ?, ?, ?, ?)");
    $stmt->bindParam(1, $detalii['nume']);
    $stmt->bindParam(2, $detalii['prenume']);
    $stmt->bindParam(3, $detalii['username']);
    $stmt->bindParam(4, md5(md5($detalii['parola'] . SIGURANTA_PAROLE) . SIGURANTA_PAROLE));
    $stmt->bindParam(5, $detalii['email']);
    $stmt->bindParam(6, $detalii['rol'], PDO::PARAM_INT);
    $stmt->bindParam(7, $detalii['status'], PDO::PARAM_INT);
    $stmt->bindParam(8, $ultima_logare);    
    $stmt->execute(); 

    $id = $db->lastInsertId();
    return $id;
}

From the Manual:

Returns the ID of the last inserted row, or the last value from a sequence object, depending on the underlying driver. For example, PDO_PGSQL() requires you to specify the name of a sequence object for the name parameter.

It should be something like:

return $db->lastInsertId('yourIdColumn');

[EDIT] Update link to doc

From the PHP manual:

For example, PDO_PGSQL() requires you to specify the name of a sequence object for the name parameter.

You could also use RETURNING in the INSERT-statement and fetch the INSERT-result like a SELECT result.

Previous answers are not very clear (PDO doc too)

In postgreSQL, sequences are created when you are using the SERIAL data type.

CREATE TABLE ingredients (
  id         SERIAL PRIMARY KEY,
  name       varchar(255) NOT NULL,
);

So the sequence name will be ingredients_id_seq

$db->lastInsertId('ingredients_id_seq');