Doctrine 2 - Join data wthout relation - symfony

Question

i have this structure in my basic model:
class Value extends ...
{
/**
* #var integer $id
*
* #ORM\Column(name="id", type="integer", nullable=false)
* #ORM\Id
* #ORM\GeneratedValue(strategy="IDENTITY")
*/
private $id;
/**
* #var string $name
*
* #ORM\Column(name="name", type="string", length=255, nullable=false)
*/
private $name;
...
}
This model cant be extended from my site, but i need to add a self-referencing ManyToMany relation for reading associated data.
So i created this new model:
class ValueGrid extends ...
{
/**
* #var integer $id
*
* #ORM\Id
* #ORM\Column(name="id", type="integer", nullable=false)
* #ORM\GeneratedValue(strategy="IDENTITY")
*/
private $id;
/**
* #var integer $parentValueId
*
* #ORM\Column(name="parentValueID", type="integer", nullable=false)
*/
private $parentValueId;
/**
* #var integer $childValueId
*
* #ORM\Column(name="childValueID", type="integer", nullable=false)
*/
private $childValueId;
...
}
When i read data from "Value", i do it like this:
$builder = $this->getEntityManager()->createQueryBuilder();
$builder->select(array('value'))
->from('Value', 'value');
// Next i need to simulate the relation
$builder->addSelect(['valuegrid']);
$builder->leftJoin('ValueGrid', 'valuegrid', 'WITH', 'value.id = valuegrid.parentValueId');
It gives this output:
{"id":1,"value":"a"},
null,
{"id":2,"value":"b"},
null,
{"id":3,"value":"c"},
{"id":1,"parentValueId":1,"childValueId":2},
{"id":4,"value":"d"},
null,
{"id":5,"value":"e"},
null
But it should be this format:
{"id":1,"value":"a", "valuegrid":null},
{"id":2,"value":"b", "valuegrid":null},
{"id":3,"value":"c", "valuegrid":{"id":1,"parentValueId":1,"childValueId":2}},
{"id":4,"value":"d", "valuegrid":null},
{"id":5,"value":"e", "valuegrid":null},
Anyone has some suggestions?
I really dont know why my approach does not work..
Thansk and Greetings!