How to bind selects in symfony?

Question

symfony

Good evening.
There are several select forms (countries, region, city), tell me how to connect these selects with each other so that when choosing a country, there is a selection of the corresponding regions and cities.
P.Y. Thanks in advance.
formType

->add('city', EntityType::class, array(
                    'class' => 'AppBundle:Countries',
                    'choice_label' => 'name',
                    'expanded' => false,
                    'multiple' => false,

                    'label' => 'Выбрать страну',
                    'attr' => array(
                        'class' => 'form-control',
                        'style' => 'margin-bottom: 15px'
                    )
                ))

->add('city', EntityType::class, array(
                    'class' => 'AppBundle:Region',
                    'choice_label' => 'name',
                    'expanded' => false,
                    'multiple' => false,

                    'label' => 'Выбрать регион',
                    'attr' => array(
                        'class' => 'form-control',
                        'style' => 'margin-bottom: 15px'
                    )
                ))

->add('city', EntityType::class, array(
                    'class' => 'AppBundle:City',
                    'choice_label' => 'name',
                    'expanded' => false,
                    'multiple' => false,

                    'label' => 'Выбрать город',
                    'attr' => array(
                        'class' => 'form-control',
                        'style' => 'margin-bottom: 15px'
                    )
                ))

Answer 1

For example, using a dependent field from this bundle or analogues.