How to access laravel sessions variables in payu post request - php

Question

I'm having some problems trying to access variables sessions in the confirmation page used it by payu. In the post request I can access the variables sent from the gateway like this: $state_pol = $_POST["state_pol"]; and no problem with that, I can stored the value in my data base, But when I try to do this $email = Auth::user()->email; when I do that I can't get any variable or stored values in the DB. I need to stored in the DB the cart Items and I'm using moltin Cart, so I need to do something like this:
foreach (Cart::contents() as $item) {
$citem = new Ite;
$citem->compra_id = $compra->id;
$citem->id_product = $item->id;
$citem->name = $item->name;
$citem->val_uni = $item->price;
$citem->image = $item->image;
$citem->iva = $item->tax;
$citem->qty = $item->quantity;
$citem->val_total = $item->total();
$citem->save();
}
Cart::destroy();
the methods Cart::contents() and Cart::destroy(); don't work, but just in the payu request, I tried this with paypal request and everything works correctly and I'm using the same code, I mean with the variables session.
Thanks in advance for the time and help.
I just realized that the problem is with eloquent too. I mean, I cannot get access to the DB, I cannot do something like this $user = User::where('id','=',1)->first(); I tried with query builder but it didn't work.