Symfony 3 form many-to-many

Question

I'm trying to create a form where I can place an order. My database schema looks like this:

I would like to have a form like this:

This is what I have so far:

$order = new Order();

$form = $this->createFormBuilder($order)
    ->add('naam', TextType::class)
    ->add('email', EmailType::class)
    ->add('phoneNumber', TextType::class)
    ->add('dateTakeout', DateType::class)
    ->add('hourTakeout', DateType::class)
    ->add('save', SubmitType::class, array('label' => 'Verzenden'))
    ->getForm();

But I'm stuck with adding the products to my form. How can I do this?

UPDATE:

The connection of my product and category is like this:

I have a Category entity with id, name, enabled and parentCategoryId.

In my Product entity I have a category property.

I would like to show the categories and products like this:

Answer 1

Add this to your form:

use Symfony\Component\Form\Extension\Core\Type\IntegerType;
...
->add('product_A', IntegerType::class)
->add('product_B', IntegerType::class)
->add('product_C', IntegerType::class)
->add('product_D', IntegerType::class)

This is an Integer, so you can simply call:

$prodA_amount = $form->get('product_A')->getData();

to get the value...