Domain\Matter\Matter::lessons PHP Method

    public function lessons()
    {
        return $this->belongsToMany(Lesson::class, 'matter_lesson');
    }

 /**
  * Associate lessons.
  * @param  Matter $matter
  * @param  array     $lessons
  */
 public function associateLessons(Matter $matter, array $lessons)
 {
     $ids = [];
     foreach ($lessons['lessons'] as $lesson) {
         $ids[] = $lesson['id'];
     }
     $matter->lessons()->sync($ids);
 }