How to ManyToMany and OneToMany in Symfony and Doctrine?

Question

I find the documentation very poor when it comes to explaining the creation of relationships between entities. So, i\'ll have to ask for help to my fellow StackExchangers. So, i

Answer 1

Sure thing. First thing to understand is that there is no "one way" to do this. Doctrine gives a lot of flexibility in terms of how you define the relationship - even if multiple definitions produce the exact same DDL (and this is important to understand - some of the mapping choices only effect the object-side of the ORM, not the model-side)

Here's your Users/Groups/Permissions example, which are actually all many-to-many associations (I excluded all non-relevant but required code, like PK column definition)

groups = new ArrayCollection();
    $this->permissions = new ArrayCollection();
  }
}

/**
 * @ORM\Entity
 */
class Group
{
  /**
   * Many-To-Many, Unidirectional
   *
   * @var ArrayCollection $permissions
   *
   * @ORM\ManyToMany(targetEntity="Permission")
   * @ORM\JoinTable(name="group_has_permission",
   *      joinColumns={@ORM\JoinColumn(name="group_id", referencedColumnName="id")},
   *      inverseJoinColumns={@ORM\JoinColumn(name="permission_id", referencedColumnName="id")}
   * )
   */
  protected $permissions;

  public function __construct()
  {
    $this->permissions = new ArrayCollection();
  }
}

/**
 * @ORM\Entity
 */
class Permission {}

If you have questions about what's going on here, let me know.

Now, to your second example

tags = new ArrayCollection();
    $this->comments = new ArrayCollection();
  }
}

/**
 * @ORM\Entity
 */
class Comment
{
  /**
   * Many-To-One, Bidirectional
   *
   * @var Ticket $ticket
   *
   * @ORM\ManyToOne(targetEntity="Ticket")
   * @ORM\JoinColumn(name="ticket_id", referencedColumnName="id")
   */
  protected $ticket=null;
}

/**
 * @ORM\Entity
 */
class Tag {}

/**
 * @ORM\Entity
 */
class Category {}

As before, let me know if you want any of this explained.

P.S. None of this was actually tested, I just kinda banged it out in my IDE real fast. There might be a typo or two ;)