One option is to download the pre-built zip package. That way you won't have to use composer.

I'd however recommend you to switch to a server where you have more control on the command line. That will make the site maintenance much easier in the long run.

Thanks for the reply. Of course, to get the "connection" between book and review it is possible to deal with containers or relationships. But I want to change the description of the book (not the review), even if I'm not the owner of it (and as "a" user I'm an admin neither)...

You can disable the access control on the book entity temporarily within the review add/edit action:

$access = elgg_set_ignore_access(true);

$book->description = "Updated description";

elgg_set_ignore_access($access);

You have to assign the correct book entity to $books depending on how you implement the connection between book and review before these lines of codes. If the permission to change the book description depends on some condition, you should include these lines within an if-clause that checks this conditions.

Yeah, that looks good and should work for my purposes.

Danke :)