On this page:
http://developers.facebook.com/docs/opengraph/using-app-tokens/
It describes how to get the app access token, yet the token it returns is different than the one in the open Graph “Get Code” example. The latter is the only one that works. How can I get the second access token using the API? When I try to use the first example, I basically get something back that looks like “application ID|secret key” which is different than the real access token.
as documentation states, you will get
string back from the API call. Even though it LOOKS like “application ID|secret key HASH” – it is a valid access token you can use to publish to user’s wall. You can verify it’s a proper access token using Debug toll from FB: https://developers.facebook.com/tools/debug – just paste the token there.
The reason it might not work for you is because you are trying to publish something to the user’s wall who did not authorize your app. Look here: https://developers.facebook.com/docs/reference/javascript/ – for example of how to use your app ID to make user authorize the app. You need to request publish_stream permission for your app from user in order to be able to publish as the app to the user’s wall.
And going back to the documentation:
hope that helps.