on my site right now I\'m trying to have it post to a users wall a media file.
I had it working on the old api before, but now I\'m trying to get it working on the new
First of all, don't confuse APIs with SDKs. The newest PHP SDK is capable of communicating with both the new Graph API and the old REST API.
And you are using the new SDK, since Facebook::$api_client
doesn't exist in the new SDK.
Secondly, as is usual with most tutorials, they only show you a snapshot of the full features of a system. See here for more details about publishing with the Graph API.
However, you can still use the old API to publish your message like so
$facebook->api( array(
'method' => 'stream.publish'
, 'target_id' => $facebook->getUser()
, 'message' => $message
, 'attachment' => $attachment
, 'action_links' => $action_links
) );