Relacions molts a molts

php bin/console make:entity

 Class name of the entity to create or update (e.g. VictoriousPizza):
 > Rating

 created: src/Entity/Rating.php
 created: src/Repository/RatingRepository.php

 Entity generated! Now let's add some fields!
 You can always add more fields later manually or by re-running this command.

 New property name (press <return> to stop adding fields):
 > user

 Field type (enter ? to see all types) [string]:
 > relation

 What class should this entity be related to?:
 > User

What type of relationship is this?
 ------------ ------------------------------------------------------------------ 
  Type         Description                                                       
 ------------ ------------------------------------------------------------------ 
  ManyToOne    Each Rating relates to (has) one User.                            
               Each User can relate to (can have) many Rating objects            

  OneToMany    Each Rating can relate to (can have) many User objects.           
               Each User relates to (has) one Rating                             

  ManyToMany   Each Rating can relate to (can have) many User objects.           
               Each User can also relate to (can also have) many Rating objects  

  OneToOne     Each Rating relates to (has) exactly one User.                    
               Each User also relates to (has) exactly one Rating.               
 ------------ ------------------------------------------------------------------ 

 Relation type? [ManyToOne, OneToMany, ManyToMany, OneToOne]:
 > ManyToOne

 Is the Rating.user property allowed to be null (nullable)? (yes/no) [yes]:
 > no

 Do you want to add a new property to User so that you can access/update 
 Rating objects from it - e.g. $user->getRatings()? (yes/no) [yes]:
 > yes

 A new property will also be added to the User class so that you can access the 
  related Rating objects from it.

 New field name inside User [ratings]:
 > ratings

 Do you want to activate orphanRemoval on your relationship?
 A Rating is "orphaned" when it is removed from its related User.
 e.g. $user->removeRating($rating)

 NOTE: If a Rating may *change* from one User to another, answer "no".

 Do you want to automatically delete orphaned App\Entity\Rating objects 
 (orphanRemoval)? (yes/no) [no]:
 > no

 updated: src/Entity/Rating.php
 updated: src/Entity/User.php

 Add another property? Enter the property name (or press <return> to stop 
  adding fields):
 > movie

 Field type (enter ? to see all types) [string]:
 > ManyToOne

 What class should this entity be related to?:
 > Movie

 Is the Rating.movie property allowed to be null (nullable)? (yes/no) [yes]:
 > no

 Do you want to add a new property to Movie so that you can access/update 
 Rating objects from it - e.g. $movie->getRatings()? (yes/no) [yes]:
 > yes

 A new property will also be added to the Movie class so that you can access 
 the related Rating objects from it.

 New field name inside Movie [ratings]:
 > ratings

 Do you want to activate orphanRemoval on your relationship?
 A Rating is "orphaned" when it is removed from its related Movie.
 e.g. $movie->removeRating($rating)

 NOTE: If a Rating may *change* from one Movie to another, answer "no".

 Do you want to automatically delete orphaned App\Entity\Rating objects 
  (orphanRemoval)? (yes/no) [no]:
 > no

 updated: src/Entity/Rating.php
 updated: src/Entity/Movie.php

 Add another property? Enter the property name (or press <return> to stop 
  adding fields):
 > value

 Field type (enter ? to see all types) [string]:
 > integer

 Can this field be null in the database (nullable) (yes/no) [no]:
 > no

 updated: src/Entity/Rating.php

 Add another property? Enter the property name (or press <return> to stop 
  adding fields):
 > 

  Success! 

namespace App\Entity;

use App\Repository\RatingRepository;
use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass=RatingRepository::class)
 */
class Rating
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity=User::class, inversedBy="ratings")
     * @ORM\JoinColumn(nullable=false)
     */
    private $user;

    /**
     * @ORM\ManyToOne(targetEntity=Movie::class, inversedBy="ratings")
     * @ORM\JoinColumn(nullable=false)
     */
    private $movie;

    /**
     * @ORM\Column(type="integer")
     */
    private $value;

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getUser(): ?User
    {
        return $this->user;
    }

    public function setUser(?User $user): self
    {
        $this->user = $user;

        return $this;
    }

    public function getMovie(): ?Movie
    {
        return $this->movie;
    }

    public function setMovie(?Movie $movie): self
    {
        $this->movie = $movie;

        return $this;
    }

    public function getValue(): ?int
    {
        return $this->value;
    }

    public function setValue(int $value): self
    {
        $this->value = $value;

        return $this;
    }
}

public function up(Schema $schema) : void
{
    // this up() migration is auto-generated, please modify it to your needs
    $this->addSql('CREATE TABLE rating (id INT AUTO_INCREMENT NOT NULL, user_id INT NOT NULL, 
        movie_id INT NOT NULL, value INT NOT NULL, INDEX IDX_D8892622A76ED395 (user_id), 
        INDEX IDX_D88926228F93B6FC (movie_id), PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 
        COLLATE `utf8mb4_unicode_ci` ENGINE = InnoDB');
    $this->addSql('ALTER TABLE rating 
        ADD CONSTRAINT FK_D8892622A76ED395 
        FOREIGN KEY (user_id) REFERENCES user (id)');
    $this->addSql('ALTER TABLE rating 
        ADD CONSTRAINT FK_D88926228F93B6FC 
        FOREIGN KEY (movie_id) REFERENCES movie (id)');
}

/*
 * @Table(name="rating",
 *      uniqueConstraints={
 *          @UniqueConstraint(name="IDX_USER_MOVIE_UNIQUE",
 *                  columns={"user_id", "movie_id"}
 *          )
 *      }
 * )
 */

// src/Form/RatingType.php
class RatingType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('value', ChoiceType::class,
                [   'label'=>false, 
                    'choices' => [1 => 1, 2=>2 , 3=>3, 4=>4, 5=>5],
                    'placeholder'=>'Select a value'
                ])
        ;
    }
   ...
}

 /**
     * @Route("/movies/{id}", name="movies_show", requirements={"id"="\d+"})
     */
    public function show(Movie $movie, Request $request)
    {
        $user = $this->getUser();

        $ratingRepository = $this->getDoctrine()->getRepository(Rating::class);
        // we find a related rating
        $ratings = $ratingRepository->findBy(["movie"=>$movie, "user"=>$user]);

        // if not we created a new one
        if (empty($ratings)) {
            $rating = new Rating();
            $rating->setMovie($movie);
            $rating->setUser($user);
        }
        // if yes we extract the first element from the returned array
        else
            $rating = $ratings[0];


        $form = $this->createForm(RatingType::class, $rating);

        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            $entityManager = $this->getDoctrine()->getManager();
            $entityManager->persist($rating);
            $entityManager->flush();

            $this->addFlash('success', 'Your rating has been saved!');
        }

        if ($movie) {
            return $this->render('movies_show.html.twig',
                [
                    'movie' => $movie,
                    'form' => $form->createView()
                ]
            );
        }
    }
    ...
}

{% if app.user %}
    {{ form_start(form, {attr: {class: 'form-inline'}}) }}
    {{ form_widget(form) }}
        <button type="submit" class="btn btn-primary">Rate!</button>
    {{ form_end(form) }}
{% endif %}

 public function getRating(): ?float {
        $sum = 0;
        foreach ($this->getRatings() as $rating) {
            $sum += $rating->getValue();
        }
        $count = count($this->getRatings());
        if (empty($count))
            return null;
        return ($sum/$count);
    }

<p class="text-muted">Rating: {{ movie.rating }}</p>