symfony ajax form dynamically modify - php

Question

I have the following form that contains data from the database it still WIP ( i'm missing a few fields that i didn't add yet).
The form loads data in the first select and based on that select i use ajax to populate a second select with options based on the first select ( basically the associations to the selected value). And from there again another select with certain options and so on and at the end when i submit the form i want to generate a report from database based on the data.
For the moment i'm stuck with the second field because i always get an error:
This value is not valid.
The form class:
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('survey', EntityType::class, [
'class' => SurveyManager::class,
'placeholder' => 'Choose option',
'attr' => [
'class' => 'field-change',
],
])
->add('headquarter', ChoiceType::class, [
'choices' => [],
])
->add('submit', SubmitType::class, [
'label' => 'Save',
])
;
}
I'm not reall sure how to fix the error or how should i handle this type of form. Can you help me out guys ?
Based on the answer i did this
$builder->addEventListener(
FormEvents::PRE_SUBMIT,
function (FormEvent $event) {
$form = $event->getForm();
$data = $event->getData();
$form->add('headquarter', EntityType::class, [
'class' => HeadQuarterManager::class,
'query_builder' => function(HeadQuarterManagerRepository $er) {
return $er->getHeadquarter($data['survey']);
},
]);
}
);
But i'm getting this error:
Notice: Undefined variable: data
Not really sure how to pass the data to the getHeadquarter method so i can return an array of id => name for the select.

Answer 1

When you run the function $form->isValid(), it checks against the form it built in the buildForm function. Any extra fields/value that aren't there will cause this error.
You can change this behaviour by using form events.

Answer 2

In the end this is how i did it:
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('survey', EntityType::class, [
'class' => SurveyManager::class,
'attr' => [
'class' => 'field-change',
],
])
->add('submit', SubmitType::class, [
])
->addEventListener(
FormEvents::PRE_SUBMIT,
function (FormEvent $event) {
$form = $event->getForm();
$data = $event->getData();
$modifier = $data['survey'];
$form->add('headquarter', EntityType::class, [
'class' => HeadQuarterManager::class,
'query_builder' => function (HeadQuarterManagerRepository $er) use ($modifier) {
return $er->getHeadquarter($modifier);
},
]);
}
);
}