Laravel many to many relationship with uuid returns always empty

Question

I use Laravel 5.8 and changed my model's autoincrement id to uuid. Since then I have some trouble with my many-to-many relationship that was defined between 2 of my models Event and User (with pivot table events_users).

The problem : Now when I request all element that join both table (I have 2 records in my pivot table) I always get an empty array back. When debugging the sql, I see that the where clause param is not set :

// Generated sql
select `users`.*, `events_users`.`event_id` as `pivot_event_id`, `events_users`.`user_id` as `pivot_user_id`, `events_users`.`created_at` as `pivot_created_at`, `events_users`.`updated_at` as `pivot_updated_at`
from `users`
inner join `events_users` on `users`.`id` = `events_users`.`user_id`
where `events_users`.`event_id` = ?

// Bindings :
Array
(
    [0] => 
)

Has someone any clue what I'm missing here ?

Here are the definition of my models :

class Event extends Model
{
    protected $primaryKey = 'id';
    protected $keyType = 'string';
    public $incrementing = false;

// here some other model methods, fillable property, etc.


public function users()
{
    return $this
        ->belongsToMany(User::class, 'events_users', 'event_id', 'user_id')
        ->withTimestamps();
}

}

Same declaration for User model, but with relation

public function events()
{
    return $this
        ->belongsToMany(Event::class, 'events_users', 'user_id', 'event_id')
        ->withPivot(['created_at', 'updated_at']);
}

Then I retrieve the relations from the service with :

public function getSubscriptions($eventId)
{
    $eventId = 'a1b7c5d6-8f86-44f4-f31a-46e32917d5c0'; // for debug purpose only
    $event = Event::find($eventId);

    foreach ($event->users as $user) {
        print_r($user); die; // It never loops here as its length is 0 but should be 2...
    }

    \DB::listen(function ($query) {
        print_r($query->sql);
        print_r($query->bindings);
        // $query->time
    });

    $subscriptions = $event
        ->users()
        ->get();
    die;

    return $subscriptions;
}

My DB contains the records

Answer 1

The problem was about another declaration in my models where I list the property. I've initialized an id property there, which is probably in conflict with the uuid type or I don't know exactly what cause this drama... Anyway, removing this line let the app work correctly.

/**
 * @var array
 * Rules used for fields validation
 */
public $rules = array(
    'title'       => 'required|string|max:255',
    'start_date'  => 'required|date|date_format:Y-m-d',
    'end_date'    => 'required|date|date_format:Y-m-d|after_or_equal:start_date',
    'location'    => 'string|max:254',
    'latitude'    => 'numeric',
    'longitude'   => 'numeric'
);

public $id          = "";  // This is the line that create the bug... Remove it and it works !
public $title       = "";
public $start_date  = "";
public $end_date    = "";
public $location    = "";
public $latitude    = "";
public $longitude   = "";