Symfony ManyToMany setter return wrong data - php

Question

I have relation User to Coupon ManyToMany.
User have many coupons and coupon may belong to many users.
When I call the method $coupon->getUsers(), I get coupon (PersistentCollection).
And when I call the method $user->getCoupon(), I get user (PersistentCollection).
User entity:
/**
* #ORM\ManyToMany(targetEntity="App\Entity\Coupon", inversedBy="users")
*/
private $coupon;
public function __construct()
{
$this->coupon = new ArrayCollection();
}
/**
* #return Collection|Coupon[]
*/
public function getCoupon(): Collection
{
return $this->coupon;
}
public function addCoupon(Coupon $coupon): self
{
if (!$this->coupon->contains($coupon)) {
$this->coupon[] = $coupon;
}
return $this;
}
public function removeCoupon(Coupon $coupon): self
{
if ($this->coupon->contains($coupon)) {
$this->coupon->removeElement($coupon);
}
return $this;
}
Coupon entity:
/**
* #ORM\ManyToMany(targetEntity="App\Entity\User", mappedBy="coupon")
*/
private $users;
public function __construct()
{
$this->users = new ArrayCollection();
}
/**
* #return Collection|User[]
*/
public function getUsers(): Collection
{
return $this->users;
}
public function addUser(User $user): self
{
if (!$this->users->contains($user)) {
$this->users[] = $user;
$user->addCoupon($this);
}
return $this;
}
public function removeUser(User $user): self
{
if ($this->users->contains($user)) {
$this->users->removeElement($user);
$user->removeCoupon($this);
}
return $this;
}
When I run this code:
namespace App\Controller;
use App\Entity\Coupon;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Routing\Annotation\Route;
class TestController extends AbstractController
{
/**
* #Route("/test", name="test")
*/
public function index()
{
$coupon = $this->getDoctrine()->getRepository(Coupon::class)->find(1);
dump($coupon->getUsers());die;
}
}
I get:
screenshot
Why I get a coupon and not a list of users?

Answer 1

On top of what Jakumi wrote, in the controller you can also do
$coupon = $this->getDoctrine()->getRepository(Coupon::class)->find(1);
$users = $coupon->getUsers();
$users->initialize();
Now when you dump($users) the collection should not be empty.
To add to that, I believe you have your mapping wrong. In your Many-To-Many relation the User is the owning side and Coupon is the inversed side, however it is the public function addUser(User $user) in the Coupon entity that does the owning side's job. You should either change the sides (change the mappedBy in Coupon to inversedBy and the other way around in the User) or make sure that User does:
public function addCoupon(Coupon $coupon): self
{
if (!$this->coupon->contains($coupon)) {
$coupon->addUser($this);
$this->coupon[] = $coupon;
}
return $this;
}
and the Coupon does:
public function addUser(User $user): self
{
if (!$this->users->contains($user)) {
$this->users[] = $user;
}
return $this;
}
Of course the removeUser and removeCoupon methods should be dealth with accordingly.

Answer 2

PersistentCollections conceptually are supposed to work like arrays and are the way of doctrine to realize lazy loading (the default). There are certain operations that will trigger the collection to be loaded from the database (such as iterating over the collection). Before that, it's property initialized will be false (as in your screenshot)
ManyToMany and OneToMany should always be realized as ArrayCollection (or some other collection, such as PersistentCollection) and should not be leaked to the outside. Instead call ->toArray() (or ->asArray(), I always forget) to return them (so, inside getUsers() or getCoupons() respectively). Inside the entity you can just foreach over the PersistentCollection.
If you mark the ManyToMany to fetch as EAGER, it will be loaded immediately, but that might have performance impact...
And the Collection holds a reference to the object it belongs to, so you're not getting a Coupon per se, you get a collection, that still references its owner ;o)