laravel 8 session doesn't save data - laravel-8

Question

I'm trying to save an array for checkout but when i print session it gives null
namespace App\Http\Livewire;
use App\Orders;
use Livewire\Component;
use Illuminate\Support\Facades\Auth;
use Illuminate\Http\Request;
use Cart;
use Carbon\Carbon;
public function setAmountForCheckout()
{
if(session()->has('coupon'))
{
session()->put('checkout',[
'discount'=>$this->discount,
'subtotal'=>$this->subtotalAfterDiscount,
'total'=>$this->totalAfterDiscount,
]);
}
else
{
session()->put('checkout',[
'discount'=>0,
'tax'=>Cart::instance('cart')->tax(),
'subtotal'=>Cart::instance('cart')->subtotal(),
'total'=>Cart::instance('cart')->total(),
]);
session()->save();
}
}
public function placeOrder(Request $request)
{
dd(session()->get('checkout'));
$this->validate([
'first_name' => 'required|min:4|string',
'Phone_number' => 'required|digits:11'
]);
$order=new Orders();
$order->user_id=Auth::id();
$order->cust_name=$this->first_name;
$order->phone=$this->Phone_number;
$order->subtotal=session()->get('checkout')['subtotal'];
$order->discount=session()->get('checkout')['discount'];
$order->total=session()->get('checkout')['total'];
$order->status='ordered';
$order->is_shipping=$this->haveShipping ? 1:0;
foreach(Cart::instance('cart')->content() as $items)
{
$orderItem= new OrderItems();
$orderItem->product_id=$items->id;
$orderItem->price=$item->price;
$orderItem->order_id=$order->id;
$orderItem->quantity=$item->qty;
$orderItem->save();
}
if($this->haveShipping)
{
$this->validate([
'Address'=>'required|min:4',
'shipping_fee'=>'required|numeric'
]);
$order->address=$this->Address;
$order->delivery=$this->shipping_fee;
}
$order->save();
Cart::instance('cart')->destroy();
session()->forget('checkout');
}
when i remove dd it gives me the error "Trying to access array offset on value of type null"
I'm trying to find what's wrong with the session.
also i have checked the cart if it works or not but i found that it works well and delivers data.

Answer 1

Remove
session()->save();
This is not needed as per https://laravel.com/docs/8.x/session#storing-data