Symfony TagType

AddEntityChoiceListener.php

<?php

namespace AppBundle\Form\EventListener;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Doctrine\ORM\EntityManager;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\Form\FormEvent;

class AddEntityChoiceSubscriber implements EventSubscriberInterface
{
    /**
     * @var EntityManager
     */
    protected $em;

    /**
     * The name of the entity
     *
     * @var string
     */
    protected $entityName;

    public function __construct(EntityManager $em, string $entityName)
    {
        $this->em = $em;
        $this->entityName = $entityName;
    }

    public static function getSubscribedEvents()
    {
        return [
            FormEvents::PRE_SUBMIT => 'preSubmit',
        ];
    }

    public function preSubmit(FormEvent $event)
    {
        $data = $event->getData();

        if (!is_array($data) && !($data instanceof \Traversable && $data instanceof \ArrayAccess)) {
            $data = [];
        }

        // loop through all values
        $repository = $this->em->getRepository($this->entityName);
        $choices = array_map('strval', $repository->findAll());
        $className = $repository->getClassName();
        $newChoices = [];
        foreach($data as $key => $choice) {
            // if it's numeric we consider it the primary key of an existing choice
            if(is_numeric($choice) || in_array($choice, $choices)) {
                continue;
            }
            $entity = new $className($choice);
            $newChoices[] = $entity;
            $this->em->persist($entity);
        }
        $this->em->flush();

        // now we need to replace the text values with their new primary key
        // otherwise, the newly added choice won't be marked as selected
        foreach($newChoices as $newChoice) {
            $key = array_search($newChoice->__toString(), $data);
            $data[$key] = $newChoice->getId();
        }

        $event->setData($data);
    }
}

demo.html.twig

{{ form(form) }}
<script>
  const select = document.querySelector('.js-select2');
  $(select).select2({
    tags: true,
  });
</script>

DemoType.php

<?php

namespace AppBundle\Form\Type;

use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\OptionsResolver\OptionsResolver;

class DemoType extends AbstractNoteType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('tags', TagType::class, [
                'required' => true,
                'class' => 'AppBundle:Tag',
                'multiple' => true,
                'attr' => [
                    'class' => 'js-select2',
                ],

            ])
        ;

        parent::buildForm($builder, $options);
    }
}

Tag.php

<?php

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * @ORM\Entity
 * @ORM\Table
 */
class Tag
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=50, nullable=false, unique=true)
     * @Assert\NotBlank()
     */
    protected $value = '';

    public function __construct(string $value = '')
    {
        $this->value = $value;
    }

    /**
     * @return int|null
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * @param string $value
     */
    public function setValue(string $value)
    {
        $this->value = $value;

        return $this;
    }

    /**
     * @return string
     */
    public function getValue(): string
    {
        return $this->value;
    }

    /**
     * @return string
     */
    public function __toString(): string
    {
        return $this->value;
    }
}

TagType.php

<?php

namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use AppBundle\Form\EventListener\AddEntityChoiceSubscriber;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;

class TagType extends AbstractType
{
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $subscriber = new AddEntityChoiceSubscriber($options['em'], $options['class']);
        $builder->addEventSubscriber($subscriber);
    }

    /**
     * {@inheritdoc}
     */
    public function getParent()
    {
        return EntityType::class;
    }

    /**
     * {@inheritdoc}
     */
    public function getName()
    {
        return 'tag';
    }
}