Laravel 5.3 belongsTo relation on same table shows no result - eloquent

Question

I'd like to make a relationship on the same table but I'm not sure it's possible...
I have a table jobs with the fields id, name and parent_id. I want to get some jobs and their parent (and their own parent if they have one, etc.).
Here's my model :
class Job extends Model
{
public function jobParent()
{
return $this->belongsTo('App\Job', 'parent_id');
}
}
In my controller I do that :
$select = Job::take(10)
->with('jobParent')
->get();
I displayed the queries and I can see the one for the relationship :
select * from jobs where id in (?, ?, ?)
I have 3 parents for my 10 jobs so it seems right but it returns parent: null for each of my jobs...
Do you see what I'm missing ?
I added this to my request because I want also the parent of the parent :
->with(['jobParent' => function($query) {
$query->with('jobParent');
}]);
I can see the two queries so it does works, it just doesn't display !
select * from jobs where id in (?, ?, ?)
select * from jobs where id in (?, ?)
I output my results this way :
$return = [
'success' => 1,
'totalCount' => $totalCount,
'nextOffset' => $offset+$nb,
'jobs' => $jobs
];
$code = 200;
return response()->json($return, $code);
Wich gives me this :
{
"success": 1,
"totalCount": 10706,
"nextOffset": 10,
"jobs": [
{
"name": "xxx",
"parent_id": 15,
"job_parent": null
}, ...
I tried to do a foreach of my jobs and a var_dump($job->jobParent) but it says NULL as well...
I just don't get why it doesn't store the results...

Answer 1

I figured it out : job.id is a string, I casted it in my model and it works fine :
protected $casts = ['id' => 'string'];