Multi Step Form Type and Wizard

ExampleController.php

<?php

    public function __invoke(Request $request): Response
    {
        $step = $request->query->getInt('step', 1);
        $helper = new WizardHelper($request, clearExistingData: 1 === $step);
        $data = $this->getData($helper->getAllData());
      
        $form = $this->formFactory->create(ExampleFormType::class, $data, options: [
            'activeStep' => $step,
        ]);

        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            /** @var array<string, mixed> $formData */
            $formData = $form->getData();

            $helper->saveStep($formData);

            if ($helper->hasNext($form, $step)) {
                return new RedirectResponse(
                    $this->urlGenerator->generate('my_route', ['step' => $step + 1]),
                );
            }

            $allData = $helper->getAllData();
          
            // TODO save

            return new RedirectResponse(
                $this->urlGenerator->generate('my_route', ['send' => 'true']),
            );
        }

        $formView = $form->createView();

        return new Response(
            // TODO
        );
    }
}

ExampleFormType.php

<?php

class ExampleFormType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder->add('details', StepFormType::class, [
            'label' => 'app.details',
            'activeStep' => $options['activeStep'],
            'step' => ++$stepCounter,
            'fields' => function (FormBuilderInterface $builder) {
                // my fields
            },
            'block_prefix' => 'details',
        ]);
      
        $builder->add('configuration', StepFormType::class, [
            'label' => 'app.configuration',
            'activeStep' => $options['activeStep'],
            'step' => ++$stepCounter,
            'fields' => function (FormBuilderInterface $builder) {
                // my fields
            },
            'block_prefix' => 'details',
        ]);
    }
}

StepFormType.php

<?php

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\Options;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Webmozart\Assert\Assert;

class StepFormType extends AbstractType
{
    final public const BLOCK_PREFIX = 'step';

    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $fieldCallable = $options['fields'];
        Assert::isCallable($fieldCallable);
        $fieldCallable($builder);
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefault('isApi', false);
        $resolver->setRequired('step');
        $resolver->setAllowedTypes('step', ['int']);
        $resolver->setRequired('activeStep');
        $resolver->setAllowedTypes('activeStep', ['int']);
        $resolver->setRequired('fields');
        $resolver->setAllowedTypes('fields', ['callable']);
        $resolver->setDefault('inherit_data', true);
        $resolver->setNormalizer('disabled', fn (Options $options) => $options['step'] !== $options['activeStep']);
    }

    public function getBlockPrefix(): string
    {
        return self::BLOCK_PREFIX;
    }
}

WizardHelper.php

<?php

/**
 * @experimental
 */
final class WizardHelper
{
    private readonly string $key;
    private readonly SessionInterface $session;

    public function __construct(
        Request $request,
        bool $clearExistingData,
    ) {
        $this->key = 'wizward_' . $request->attributes->get('_route', '');
        $this->session = $request->getSession();
        if ($clearExistingData) {
            $this->clearAllData();
        }
    }

    /**
     * @return array<string, mixed>
     */
    public function getAllData(): array
    {
        /** @var array<string, mixed> */
        return $this->session->get($this->key, []);
    }

    public function clearAllData(): void
    {
        $this->session->remove($this->key);
    }

    /**
     * @param array<string, mixed> $data
     */
    public function saveStep(array $data): void
    {
        $data = \array_merge($this->getAllData(), $data);

        $this->session->set($this->key, $data);
    }

    public function hasNext(FormInterface $form, int $step): bool
    {
        $allSteps = 0;

        foreach ($form->all() as $key => $child) {
            if ($child->getConfig()->getType()->getInnerType() instanceof StepType) {
                ++$allSteps;
            }
        }

        return $allSteps > $step;
    }

    /**
     * @return array<int, array{
     *     label: string,
     *     title: string,
     *     description: string,
     *     activeStep: bool,
     * }>
     */
    public function getProgressItems(FormInterface $form, int $step): array
    {
        $progressItems = [];

        $i = 0;
        foreach ($form->all() as $key => $child) {
            if ($child->getConfig()->getType()->getInnerType() instanceof StepType) {
                /** @var string $label */
                $label = $child->getConfig()->getOption('label') ?? '';
                /** @var string $contentTitle */
                $contentTitle = $child->getConfig()->getOption('contentTitle') ?? '';
                /** @var string $contentDescription */
                $contentDescription = $child->getConfig()->getOption('contentDescription') ?? '';

                $progressItems[] = [
                    'label' => $label,
                    'title' => $contentTitle,
                    'description' => $contentDescription,
                    'activeStep' => (++$i === $step),
                ];
            }
        }

        return $progressItems;
    }
}