How to specify multiple sections when adding a product?

Question

symfony

Hello.
Symfony 4.2.3. When adding a product, I want to display several drop-down lists with the same name, i.e. categories[0], categories[1], etc. to specify the sections in which the added product will be located. Can't figure out how to implement this?
entity category:

class Category
{
    /**
     * @ORM\ManyToMany(targetEntity="App\Entity\Product", inversedBy="categories")
     * @ORM\JoinTable(name="categories_products", joinColumns={@ORM\JoinColumn(name="category_id", referencedColumnName="id")}, inverseJoinColumns={@ORM\JoinColumn(name="product_id", referencedColumnName="id")})
     */
    private $products;
}

entity product:

class Product
{
    /**
     * @ORM\ManyToMany(targetEntity="App\Entity\Category", mappedBy="products")
     */
    private $categories;

    /**
     * Product constructor.
     */
    public function __construct()
    {
        $this->categories = new ArrayCollection();
    }

    /**
     * @return ArrayCollection
     */
    public function getCategories(): ArrayCollection
    {
        return $this->categories;
    }
}

Answer 1

bears , thanks for your help. So far I did it the way you suggested. There was an idea how to implement what I wanted, but I need to try. The page https://symfony.com/doc/current/reference/forms/ty... has a subsection called "Adding and Removing Items" that tells you how to add more to two existing fields using jQuery. But no one forbids us when adding a product, after loading the page, using the same jQuery to add one drop-down list and a link to add additional ones.