Please tell me if I\'m understanding correctly. (because I might not be.)
Before posting to the server, call FB.getLoginStatus()
on the client to get the latest access token. There is no flash when using this method and no user interaction, as it simply grabs a new access token.
FB.getLoginStatus( function ( response ) {
if ( response.authResponse ) {
var accessToken = response.authResponse.accessToken;
//post to server
};
} );