Error Exception PHP 8.1.2 9.5.1 Array to string conversion Laravel Ecommerce

Question

I'm in dire need of your assistance. I'm following a Laravel 8 Ecommerce tutorial and Im at the checkout stage.

After following all the steps and reconfirming the code a couple of times I get the error subject every time while the tutorial proceeds to success and its driving me nuts!! Pls someone help me understand where I'm going wrong. Thank you. Below is the code. All solutions will be appreciated.

Livewire relationship models Order Model:

    <?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Order extends Model
{
    use HasFactory;

    protected $table = "orders";

    public function user()
    {
        return $this->belongsTo(User::class);
    }
    public function orderItems()
    {
        return $this->hasMany(OrderItem::class);
    }

    public function shipping()
    {
        return $this->hasOne(Shipping::class);
    }

    public function transaction()
    {
        return $this->hasOne(Transaction::class);
    }
}

OrderItem

    <?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class OrderItem extends Model
{
    use HasFactory;

    protected $table = "order_items";

    public function order()
    {
        return $this->belongsTo(Order::class);
    }
}

Shipping Model

    <?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Shipping extends Model
{
    use HasFactory;

    protected $table = "shippings";

    public function order()
    {
        return $this->belongsTo(Order::class);
    }
}

Transaction Model

    <?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Transaction extends Model
{
    use HasFactory;
    protected $table = "transactions";

    public function order()
    {
        return $this->belongsTo(Order::class);
    }
}

Checkout Component

    <?php

namespace App\Http\Livewire;

use Cart;
use App\Models\Order;
use Livewire\Component;
use App\Models\Shipping;
use App\Models\OrderItem;
use App\Models\Transaction;
use Illuminate\Support\Facades\Auth;

class CheckoutComponent extends Component

{
    public $ship_to_different;

    public $firstname;
    public $lastname;
    public $mobile;
    public $email;
    public $line1;
    public $line2;
    public $city;
    public $address;
    public $country;
    public $zipcode;

    public $s_firstname;
    public $s_lastname;
    public $s_mobile;
    public $s_email;
    public $s_line1;
    public $s_line2;
    public $s_city;
    public $s_address;
    public $s_country;
    public $s_zipcode;

    public $paymentmode;
    public $thankyou;

    public function updated($fields)
    {
        $this->validateOnly($fields, [
            'firstname' => 'required',
            'lastname' => 'required',
            'mobile' => 'required|numeric',
            'email' => 'required|email',
            'line1' => 'required',
            'city' => 'required',
            'address' => 'required',
            'country' => 'required',
            'zipcode' => 'required'
        ]);

        if ($this->ship_to_different) {
            $this->validateOnly($fields, [
                's_firstname' => 'required',
                's_lastname' => 'required',
                's_mobile' => 'required|numeric',
                's_email' => 'required|email',
                's_line1' => 'required',
                's_city' => 'required',
                's_address' => 'required',
                's_country' => 'required',
                's_zipcode' => 'required',

            ]);
        }
    }
    
    public function placeOrder()
    {
        $this->validate([
            'firstname' => 'required',
            'lastname' => 'required',
            'mobile' => 'required|numeric',
            'email' => 'required|email',
            'line1' => 'required',
            'city' => 'required',
            'address' => 'required',
            'country' => 'required',
            'zipcode' => 'required'
        ]);

        $order = new Order();
        $order->user_id = Auth::user()->id;
        $order->subtotal = session()->get('checkout', ['subtotal']);
        $order->discount = session()->get('checkout', ['discount']);
        $order->tax = session()->get('checkout', ['tax']);
        $order->total = session()->get('checkout', ['total']);
        $order->firstname = $this->firstname;
        $order->lastname = $this->lastname;
        $order->mobile = $this->mobile;
        $order->email = $this->email;
        $order->line1 = $this->line1;
        $order->line2 = $this->line2;
        $order->city = $this->city;
        $order->address = $this->address;
        $order->country = $this->country;
        $order->zipcode = $this->zipcode;
        $order->status = 'ordered';
        $order->is_shipping_different = $this->ship_to_different ? 1 : 0;
        $order->save();

        

        foreach ((Cart::instance('cart'))->content() as $item) {
            $orderItem = new OrderItem();
            $orderItem->product_id = $item->id;
            $orderItem->order_id = $order->id;
            $orderItem->price = $item->price;
            $orderItem->quantity = $item->qty;
            $orderItem->save();
        }

        if ($this->ship_to_different) {
            $this->validate([
                's_firstname' => 'required',
                's_lastname' => 'required',
                's_mobile' => 'required|numeric',
                's_email' => 'required|email',
                's_line1' => 'required',
                's_city' => 'required',
                's_address' => 'required',
                's_country' => 'required',
                's_zipcode' => 'required'
            ]);

            $shipping = new Shipping();
            $shipping->order_id = $order->id;
            $shipping->firstname = $this->s_firstname;
            $shipping->lastname = $this->s_lastname;
            $shipping->mobile = $this->s_mobile;
            $shipping->email = $this->email;
            $shipping->line1 = $this->s_line1;
            $shipping->line2 = $this->s_line2;
            $shipping->city = $this->s_city;
            $shipping->address = $this->s_address;
            $shipping->country = $this->s_country;
            $shipping->zipcode = $this->s_zipcode;
            $shipping->save();
        }

        if ($this->paymentmode == 'cod') {
            $transaction = new Transaction();
            $transaction->user_id = Auth::user()->id;
            $transaction->order_id = $order->id;
            $transaction->mode = 'cod';
            $transaction->status = 'pending';
            $transaction->save();
        }

        $this->thankyou = 1;
        Cart::instance('cart')->destroy();
        session()->forget('checkout');
    }

    public function verifyForCheckout()
    {
        if (!Auth::check()) {
            return redirect()->route('login');
        } else if ($this->thankyou) {
            return redirect()->route('thankyou');
        } else if (!session()->get('checkout')) {
            return redirect()->route('product.cart');
        }
    }

    public function render()
    {
        $this->verifyForCheckout();
        return view('livewire.checkout-component')->layout('layouts.base');
    }
}