How can I post a message to event wall via Graph API as a specific user?

Old API has this: https://developers.facebook.com/docs/reference/rest/stream.publish/, which allows me to specify uid (who is author of the post) and target_id (whose wall it is).

I can't find anything like that in current Graph API. Both https://developers.facebook.com/docs/reference/api/event/ and https://developers.facebook.com/docs/reference/api/user/ give me only an option to decide which wall I am using, but not who is the author.

E.g. user changes his RSVP to event in my application SuperFooBar and I 开发者_运维百科want to give him possibility to also specify a RSVP comment. I need to post this comment via PHP SDK to event's wall as it was him/her writing that manually. Only I can achieve is to post the comment to event's wall as SuperFooBar application :(

Could anyone help, please? Thanks!

UPDATE: Now, totally desperate, I have actually tried the deprecated REST API way to do it. And it's apparently not possible any more, at all. Even the old REST API raises following error: #200, The user isn't allowed to post to this event's wall.

Well, but the question is still relevant. Is it possible to do this somehow? Is it possible to gain permissions to do that?