[Doctrine] how to replace Many-To-Many to three entities

When you need to put new field/database columns into Many-To-Many, relationship, you will need to switch to intermediate entity. In my case it is StudentKlass.

Imagine three entities: Team - StudentTeam - Student

use Doctrine\ORM\Mapping as ORM;

class Team {
    /**
     * @ORM\OneToMany(targetEntity=StudentTeam::class, mappedBy="team", cascade={"persist"})
     */
    private $studentTeams;
    
    public function __construct() {
        $this->studentTeams = new ArrayCollection();
    }
    ...
}

class StudentTeam {
    /**
     * @ORM\ManyToOne(targetEntity=Student::class, inversedBy="teams")
     * @ORM\JoinColumn(name="student_id", referencedColumnName="id")
     */
    private $student;

    /**
     * @ORM\ManyToOne(targetEntity=Team::class, inversedBy="studentTeams")
     */
    private $team;
    ...
}

class Student {
    /**
     * @ORM\OneToMany(targetEntity=StudentTeam::class, mappedBy="student")
     */
    private $teams;
    private $name;
    private $email;
    ...

} 

Also don't forget to create getters, adders & removers!

You can use example how to use it in Symfony forms, which has example how to use nested forms:

class TeamType extends AbstractType {
    public function buildForm(FormBuilderInterface $builder, array $options) {
        $builder
            ->add('studentTeams', CollectionType::class, [
                'entry_type' => TeamStudentType::class,
                'allow_add' => true,
                'allow_delete' => true,
                'by_reference' => false,
            ]);
    ...
}

class TeamStudentType extends AbstractType {
    public function buildForm(FormBuilderInterface $builder, array $options) {
        $builder
            ->add(
                $builder
                    ->create('student', FormType::class, [
                        'data_class' => Student::class,
                    ])
                    ->add('email', TextType::class)
                    ->add('name', TextType::class)
            )
        ;
    }
}
}