Is there a way to post a session variable?

Question

I am looking to access a logged in user_id that is stored in the session, and post it in a query. So something like:

if(!empty($_SESSION['user_id'])) {
    $_POST['user_id'] = $_SESSION['user_id'];
    $ui = $_POST['user_id'];
} else {
    $errors[] = 'Please login before posting a book for sale.';
}

and then in the query:

if (empty($errors)) {
$q = 'INSERT INTO books (user_id, isbn, name, image, price) VALUES (?, ?, ?, ?, ?)';
$stmt = mysqli_prepare($dbc, $q);
mysqli_stmt_bind_param($stmt, 'isssd', $ui, $isbn, $bn, $i, $p);
mysqli_stmt_execute($stmt);

Now I already know that the first IF statement isn't correct, but I posted it like that so you PHP'ers can see what I am trying to accomplish. I am trying to figure how to take the stored variable user_id, make it sticky, and then post it in the query. Thanks!

Answer 1

Since you already have your variable stored in $_SESSION['user_id']..

Why don't you just use this:

$ui = $_SESSION['user_id'];

Answer 2

Just put session id in a variable. no need to write any POST variable. You can use like this :

$your_variable = $_SESSION['user_id'];
//according to your code you can write it
$ui = $_SESSION['user_id'];

And surely don't forget to use session_start(); at top of your page.