Deleting a self-referencing #ManyToMany connection - php

Question

I have a self-referencing entity Product:
<?php
/** #Entity #Table(name="products") **/
class Product
{
/** #Id #Column(type="integer") #GeneratedValue **/
protected $id;
/** #Column(type="string", nullable=true) **/
protected $name;
/**
* #ManyToMany(targetEntity="Product", mappedBy="connectedBy", cascade={"all"})
*/
protected $connectedWith;
/**
* #ManyToMany(targetEntity="Product", inversedBy="connectedWith", cascade={"all"})
* #JoinTable(name="connection",
* joinColumns={#JoinColumn(name="product_id", referencedColumnName="id")},
* inverseJoinColumns={#JoinColumn(name="connected_product_id", referencedColumnName="id")}
* )
*/
protected $connectedBy;
public function __construct()
{
$this->connectedWith = new \Doctrine\Common\Collections\ArrayCollection();
$this->connectedBy = new \Doctrine\Common\Collections\ArrayCollection();
}
public function getConnected()
{
return $this->connectedWith;
}
public function addConnection(Product $product)
{
$this->connectedWith->add($product);
$product->connectedBy->add($this);
}
public function removeConnection(Product $product)
{
$this->connectedBy->removeElement($product);
$this->connectedWith->removeElement($product);
}
}
Next I created two products (IDs 1 and 2) and a connection between the both products:
mysql> select * from products;
+----+------+
| id | name |
+----+------+
| 1 | NULL |
| 2 | NULL |
+----+------+
2 rows in set (0.00 sec)
mysql> select * from connection;
+------------+----------------------+
| product_id | connected_product_id |
+------------+----------------------+
| 2 | 1 |
+------------+----------------------+
1 row in set (0.01 sec)
Now I want to remove the connection with this code:
$product1 = $entityManager->find('Product', 1);
$product2 = $entityManager->find('Product', 2);
$product1->removeConnection($product2);
$entityManager->persist($product1);
$entityManager->flush();
$product3 = $entityManager->find('Product', 1);
print count($product3->getConnected()) . "\n";
As expected, the code prints 0 as its result. But when I look into the database, the connection entry still exists. What could be the cause any how could this be fixed?
I've already tried to $entityManager->persist($product2) but to no avail.

Answer 1

I researched a little more and found the solution myself:
My function removeConnection() has a bug: I removed the product from both lists, connectedBy and connectedWith, which is wrong. Instead, I should do it like in addConnection():
$this->connectedWith->removeElement($product);
$product->connectedBy->removeElement($this);