Custom collection in Doctrine

example.php

<?php
/** 
* This is a bit messy but seems to work
*/

#[Entity]
class ParentEntity
{
  #[Column]
  #[Id]
  private string $id;

  #[OneToOne(mappedBy: 'parentEntity', cascade:['all'])]
  private CustomCollection $customCollection
}

#[Entity]
class CustomCollection
{
  #[Id]
  #[OneToOne]
  #[JoinColumn('parent_entity_id', referencedColumnName: 'id')]
  private ParentEntity $parentEntity;
  
  #[ManyToMany(targetEntity: CollectionItem::class, cascade: ['all'])]
  #[JoinTable]
  #[JoinColumn(name:'parent_entity_id', referencedColumnName: 'parent_entity_id')]
  #[InverseJoinColumn(name:'id', referencedColumnName: 'id')]
  #[InverseJoinColumn(name:'f_parent_entity_id', referencedColumnName: 'parent_entity_id')]
  private Collection $items;
}

#[Entity]
class CollectionItem
{
  #[Column]
  #[Id]
  private string $id;
  
  #[Id]
  #[ManyToOne]
  #[JoinColumn(name:'parent_entity_id', referencedColumnName: 'id')]
  private ParentEntity $parentEntity;
}