yii\rbac\DbManager::getChildRoles PHP Method

    public function getChildRoles($roleName)
    {
        $role = $this->getRole($roleName);
        if (is_null($role)) {
            throw new InvalidParamException("Role \"{$roleName}\" not found.");
        }
        $result = [];
        $this->getChildrenRecursive($roleName, $this->getChildrenList(), $result);
        $roles = [$roleName => $role];
        $roles += array_filter($this->getRoles(), function (Role $roleItem) use($result) {
            return array_key_exists($roleItem->name, $result);
        });
        return $roles;
    }