Cannot get doctrine 2 many-to-many relationships to work - doctrine-orm

Question

I have 2 entities - a User and a Tag.
This is my user:
<?php
namespace Project\Model;
/**
* #Entity
* #Table(name="users")
* #InheritanceType("JOINED")
* #DiscriminatorColumn(name="discr", type="string")
* #DiscriminatorMap({"user" = "User", "client" = "Client", "staff" = "Staff"})
**/
class User implements \JsonSerializable {
/** #Id #Column(type="integer") #GeneratedValue **/
protected $id;
/** #Column(type="string", name="first_name") **/
protected $firstName;
/**
* #ManyToMany(targetEntity="Project\Model\Tag", inversedBy="users")
* #JoinTable(name="user_tags")
**/
protected $tags;
/**
* Construct a new user.
*/
public function __construct() {
$this->tags = new \Doctrine\Common\Collections\ArrayCollection();
}
// Getters
public function getId() {
return $this->id;
}
public function getFirstName() {
return $this->firstName;
}
public function getTags() {
return $this->tags;
}
// Setters
public function setFirstName($firstName) {
$this->firstName = $firstName;
}
/**
* Add a tag to a user.
* #param Tag
*/
public function addTag(Tag $tag) {
$tag->addUser($this);
$this->tags[] = $tag;
}
}
This is my Tag:
<?php
namespace Project\Model;
/**
* #Entity
* #Table(name="tags")
**/
class Tag implements \JsonSerializable {
/** #Id #Column(type="integer") #GeneratedValue **/
protected $id;
/** #Column(type="string") **/
protected $tag;
/**
* #ManyToMany(targetEntity="Project\Model\User", mappedBy="tags")
*/
protected $users;
public function __construct() {
$this->users = new \Doctrine\Common\Collections\ArrayCollection();
}
// Getters
public function getId() {
return $this->id;
}
public function getTag() {
return $this->tag;
}
// Setters
public function setTag($tag) {
$this->tag = $tag;
}
public function addUser(User $user) {
$this->users[] = $user;
}
}
If I create a new Tag, a new User, add the Tag to the User, then call the getTag() method, it returns nothing -- can anybody help me out where I am going wrong?
$tag = new Tag();
$tag->setTag('Foo');
$entityManager->persist($tag);
$user = new User();
$user->addTag($tag);
$entityManager->persist($user);
$entityManger->flush();
var_dump($user->getTags());

Answer 1

I think the problem might come from your ManyToMany relation. You use
#ManyToMany(targetEntity="Tag", inversedBy="users")
whereas you should have something like (assuming you are using Symfony 2 of course) :
#ManyToMany(targetEntity="AppBundle\Entity\Tag")
Also, you use a inversedBybut no mappedBy, so your mapping is invalid.
And this last one is more of a detail, but name a property "tag" inside a Tag class is not the cleanest. Maybe change it to "name".

Answer 2

In your Tag class, you reference the User class using:
/**
* #ManyToMany(targetEntity="Bix\Model\User", mappedBy="tags")
*/
Should "Bix" be "Project"? Unless this was a typo in your question, that woud cause issues.
One side should "own" the association and be responsible for setting the inverse association when it is added.
<?php
// Assuming that the User is the "owning side".
class User {
// Mappings as you have them, minus the "Bix" namespace thing.
public function getTags()
{
return $this->tags;
}
public function addTag(Tag $tag)
{
$tag->addUser($this);
$this->tags->add($tag);
}
public function removeTag(Tag $tag)
{
$tag->removeUser($this);
$this->tags->removeElement($tag);
}
}
class Tag {
// Mappings as you have them, minus the "Bix" namespace thing.
public function getUsers()
{
return $this->users;
}
public function addUser(User $user)
{
$this->users->add($user);
}
public function removeUser(User $user)
{
$this->users->removeElement($user);
}
}