Aws\Credentials\CredentialProvider::chain PHP Метод

    public static function chain()
    {
        $links = func_get_args();
        if (empty($links)) {
            throw new \InvalidArgumentException('No providers in chain');
        }
        return function () use($links) {
            /** @var callable $parent */
            $parent = array_shift($links);
            $promise = $parent();
            while ($next = array_shift($links)) {
                $promise = $promise->otherwise($next);
            }
            return $promise;
        };
    }