Persist array store in session symfony - arrays

Question

It's been several days since I've been blocking to persist items from an order into session to database.
I stock articles in session in an array and I do not know how to persist the array. I try to convert the array into an object, I can not. This is my service:
public function addArticle($id)
{
$sessionCart = $this->session;
$article = $this->doctrine->getRepository('AppBundle:Article')->find($id);
$cart = $sessionCart->get('cart');
$cart[] = $article;
$sessionCart->set('cart', $cart);
// use later for delivery
$sessionCart->get('commande');
return $sessionCart;
}
public function panier()
{
$articles = $this->session->get('cart');
return $articles;
}
public function delivery(Request $request)
{
$commande = new Commande();
$articles = $this->session->get('cart');
$form = $this->form->create(CommandeType::class, $commande);
if ($request->isMethod('POST') && $form->handleRequest($request)->isValid())
{
$data = $form->getData();
$this->session->set('commande', $data);
$response = new RedirectResponse('payment');
$response->send();
}
return [$form, $articles];
}
public function payment(Request $request)
{
$articles = $this->session->get('cart');
$commande = $this->session->get('commande');
if ($request->isMethod('POST')) {
$em = $this->doctrine;
$em->persist($articles);
$em->persist($commande);
$em->flush();
}
return[$articles, $commande];
}
Error : "EntityManager#persist() expects parameter 1 to be an entity object, array given."
The order is persisted but not the items.
Thanks

Answer 1

I can't understand these two lines
$cart = $sessionCart->get('cart');
$cart[] = $article;
$sessionCart->set('cart', $cart);
$cart is an array and should be an entity isn't it ?
The persist is waiting for an entity,
maybe you can persist in a foreach loop:
foreach($articles as $article){
$em->persist($article);
}
or use a doctrineCollection instead of an array