get ID of current inserted ID [duplicate]

Question

When you go to my website, i have a homepage with a button: Start enquete. When you click that button, you will see the enquete.

In the meantime, when you clicked that button. A ID has been inserted in the database.

Index.php:

        <form method="POST">
            <input type="hidden" name="x">
            <input type="submit" value="Go to enquete">
        </form>
<?php
    if(isset($_POST['x'])){
        $test = $database->insert_user_id();
        //header('Location: enquete/page1.php');
    }

And the function:

function insert_user_id(){
        $sql = "INSERT INTO user (user_id) VALUES (DEFAULT)";
        $sth = $this->pdo->prepare($sql);
        $sth->execute();
        return $this->pdo->('user_id');
}

the return $this->pdo->('user_id'); is something i'm testing with! Now my question is. How do i return the last inserted id from the table user.
I need to show it on the next page. (See //header).

I can't do this with a other query like: SELECT MAX ID or GetLastInsertId.
This becuase, when some one else also starts the enquete, he will have an other id all of the sudden.

How do i let the person keep the correct id.

Answer 1

Use PDO::lastInsertId

$this->pdo->lastInsertId();

Answer 2

Try this. Manual PDO::lastInsertId

$stmt = $db->prepare("...");
$stmt->execute();
$id = $db->lastInsertId();