Cart.php

<?php

namespace App;

class Cart
{
    private $cart;

    public function __construct()
    {
        if ($this->get() === null)
            $this->set([]);

        $this->cart = $this->get();
    }

    public function add(Product $product): void
    {
        $item = [
            'id' => $product->id,
            'name' => $product->name,
            'price' => $product->price,
            'quantity' => 1,
        ];

        if (!$this->exists($item)) {
            array_push($this->cart, $item);
        }

        $this->set($this->cart);
    }

    public function remove(int $productId): void
    {
        array_splice($this->cart, array_search($productId, array_column($this->cart, 'id')), 1);

        $this->set($this->cart);
    }

    public function clear(): void
    {
        $this->set([]);
    }

    public function get(): ?array
    {
        return request()->session()->get('cart');
    }

    private function set($cart): void
    {
        request()->session()->put('cart', $cart);
    }
}