ldc-dam/app/Models/Recherche.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Recherche extends Model
{
    /**
     * Get the sujet that owns the recherche.
     */
    public function sujet()
    {
        return $this->belongsTo('App\Models\Sujet', 'sujet_id');
    }

    /**
     * Get the user that owns the recherche.
     */
    public function user()
    {
        return $this->belongsTo('App\Models\User', 'id');
    }
}