osb/app/Http/Controllers/CheckoutController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;

use App\Http\Requests\CheckoutAddEdit;
use App\Models\{Checkout,Invoice};

class CheckoutController extends Controller
{
	/**
	 * Update a checkout details
	 *
	 * @param CheckoutAddEdit $request
	 * @param Checkout $o
	 * @return RedirectResponse
	 */
	public function addedit(CheckoutAddEdit $request,Checkout $o): RedirectResponse
	{
		foreach ($request->validated() as $key => $item)
			$o->{$key} = $item;

		$o->active = (bool)$request->validated('active',FALSE);

		try {
			$o->save();

		} catch (\Exception $e) {
			return redirect()
				->back()
				->withErrors($e->getMessage())->withInput();
		}

		return $o->wasRecentlyCreated
			? redirect()
				->to('a/checkout/'.$o->id)
				->with('success','Checkout added')
			: redirect()
				->back()
				->with('success','Checkout saved');
	}

	public function cart_invoice(Request $request,Invoice $o=NULL)
	{
		if ($o) {
			$request->session()->put('invoice.cart.'.$o->id,$o->id);
		}

		if (! $request->session()->get('invoice.cart'))
			return redirect()
				->to('u/home');

		return view('theme.backend.adminlte.u.invoice.cart')
			->with('invoices',Invoice::find(array_values($request->session()->get('invoice.cart'))));
	}

	public function fee(Request $request,Checkout $o): float
	{
		return $o->fee($request->post('total',0));
	}

	public function pay(Request $request,Checkout $o)
	{
		return redirect('pay/paypal/authorise');
	}
}