How to create a tag system with addition when sending a post creation - forms

Question

I'm trying to get a tag system working with symfony 6.
so I find several examples on the net but I have the impression that it is no longer relevant
I wish
Search for tags in the list of tags already saved in the database,
Or if the tag does not exist I want to create it when validating the form
I don't know how to proceed; I have read several things and tried but it does not work.
so I have a ManyToMany relationship between POST and TAGS.
When in the form I try this method:
->add('tags', SearchableEntityType::class, [
'class' => Tags::class
])
Then in the SearchableEntityType class
<?php
namespace App\Form\SearchTags;
use Doctrine\Common\Collections\Collection;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\ChoiceList\View\ChoiceView;
use Symfony\Component\Form\FormView;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
class SearchableEntityType extends AbstractType
{
public function configureOptions(OptionsResolver $resolver) {
$resolver->setRequired('class');
$resolver->setDefaults([
'compound' => false,
'multiple' => true,
]);
}
public function buildView(FormView $view, FormInterface $form, array $options) {
$view->vars['expanded'] = false;
$view->vars['placeholder'] = null;
$view->vars['placeholder_in_choices'] = false;
$view->vars['multiple'] = true;
$view->vars['preferred_choices'] = [];
$view->vars['choices'] = $this->choices($form->getData());
$view->vars['choice_translation_domain'] = null;
$view->vars['full_name'] .= '[]';
}
public function getBlockPrefix()
{
return 'choice';
}
public function choices(Collection $value) {
$x =$value
->map(fn ($d) => new ChoiceView($d, (string)$d->getId(), (string) $d))
->toArray();
return $value
->map(fn ($d) => new ChoiceView($d, (string)$d->getId(), (string) $d))
->toArray();
}
}
I have this error
Symfony\Bridge\Twig\Extension\twig_is_selected_choice(): Argument #2 ($selectedValue) must be of type array|string|null, Doctrine\ORM\PersistentCollection given, called in *var\cache\dev\twig\a5\a5b3010b2620ea40fefcaf4778f4ed00.php on line 532
Thanks a lot!