ProductList.php

<?php

class ProductList
{
    private $products;

    public function __construct(array $products = [])
    {
        $this->products = $products;
    }

    public function loadProducts(): void
    {
        $csvData = array_map('str_getcsv', file('products.csv'));
        $csvHeader = $csvData[0];
        unset($csvData[0]);

        $this->products = [];

        foreach ($csvData as $row) {
            $row = array_combine($csvHeader, $row);
            $this->products[$row['name']] = new Product($row['name'], $row['amount'], $row['type']);
        }

    }

    public function save(): void
    {

        $file = fopen("products.csv", "w");

        $header = ['name', 'amount', 'type'];
        fputcsv($file, $header);

        foreach ($this->products as $product) {
            fputcsv($file, [$product->getName(), $product->getAmount(), $product->getType()]);
        }

        fclose($file);
    }

    public function addProduct(string $name, float $amount, string $type): void
    {
        $product = new Product($name, $amount, $type);
        $this->products[$name] = $product;
        $this->save();
    }

    public function editProduct(string $name, float $amount): void
    {
        $this->products[$name]->setAmount($amount);
        $this->save();
    }

    public function removeProduct(string $name): void
    {
        unset($this->products[$name]);
        $this->save();
    }

    public function checkExistance(string $name): ?string
    {
        foreach ($this->products as $product) {
            if ($product->getName() == $name) return $product->getType();
        }
        return false;
    }

    public function showProducts(): array
    {
        $result = [];

        foreach ($this->products as $product) {
            $result[] = $product->getName() . ' | ';
            $result[] = $product->getAmount() . ' | ';
            $result[] = $product->getType() . " |\n";
        }
        return $result;
    }

}