yii\mongodb\rbac\MongoDbManager::getUserIdsByRole PHP Method

    public function getUserIdsByRole($roleName)
    {
        if (empty($roleName)) {
            return [];
        }
        $rows = (new Query())->select(['user_id'])->from($this->assignmentCollection)->where(['item_name' => $roleName])->all($this->db);
        return ArrayHelper::getColumn($rows, 'user_id');
    }