set all information of user or model to null after restore Laravel Setting null values only on certain fields

UserModel.php

// BaseModel Class

  protected $nullable = [];

  /**
   * Listen for save event
   */
  protected static function boot()
  {
    parent::boot();

    static::saving(function($model)
    {
      self::setNullables($model);
    });
  }

  /**
   * Set empty nullable fields to null
   * @param object $model
   */
  protected static function setNullables($model)
  {
    foreach($model->nullable as $field)
    {
      if(empty($model->{$field}))
      {
        $model->{$field} = null;
      }
    }
  }
  

// In my model class, e.g. Comment

  protected $nullable = ['post_id'];