Is the FB PHP SDK's getAccessToken() a reliable way to retrieve a user's auth token?

Question

So I have a FB app and in some situations I need my Javascript to load content into a div using a php file that lives in the same domain as index.php. For some of these I like to make sure that the user is still valid and/or have need of an auth token and FB user id. I achieved this by making creating an instance of the FB PHP SDK in the php file being ajax injected by the javascript and using getUser() and getAccessToken(). I have noticed, however, that sometimes inexplicably the getAccessToken() call will fail and report that it needs a valid access token to perform the action.

Is getAccessToken() a reliable (or even ideal) way to ensure a user is logged into FB or should I be doing something else (e.g. storing the access token I parse from the signed request in Javscript and passing it as a variable to the php files I am injecting)? Thanks.

Answer 1

Most reliable would probably be to get their details. I have, in hte past, had an instance of "getUser" return true, but the user has not actually logged on. So now I also get all their details and this works more reliably:

$facebook = new Facebook(array(
                            'appId' => FB_APP_ID,
                            'secret' => FB_APP_SECRET,
                            'cookie' => true
                    ));
$FB_UID=false;
try {
    $FB_UID = $facebook->getUser();
    // This verifies the user is actually logged in. teh above can return "true" but the following will crap out and throw exception
    $FB_me = $facebook->api('/me');  // 'birthday'
    // Not needed:
    // $FB_token = $facebook->getAccessToken();

} catch (FacebookApiException $e) {
    $FB_UID = false;
    $FB_me = false;
    // $FB_token = false;
}