FacebookJavaScriptLoginHelper fails to authenticate user on first page refresh - facebook

Question

I'm creating a Facebook app for mobile devices. Such application is displayed within a mobile browser, unlike Facebook canvas pages which are held in an iframe.
I'm using a mix of JS and PHP SDK to authorize and authenticate a user. The user needs to be already logged into Facebook to use my app. If not, they need to log in with Facebook login button. As a bridge between JS and PHP SDKs I'm using FacebookJavaScriptLoginHelper.
Part of my Facebook.php library doing the job:
<?php
// Initialize the SDK
FacebookSession::setDefaultApplication($this->app_id, $this->app_secret);
// Create the login helper
$this->helper = new FacebookJavaScriptLoginHelper();
try {
$this->session = $this->helper->getSession();
} catch(FacebookRequestException $ex) {
// When Facebook returns an error
} catch(Exception $ex) {
// When validation fails or other local issues
}
if ($this->session) {
// User logged in
$this->session = new FacebookSession($this->session->getToken());
}
?>
Facebook JS init:
<script type="text/javascript">
window.fbAsyncInit = function() {
FB.init({
appId: '{my app id}',
status: true,
xfbml: true,
cookie: true
});
}
FB.getLoginStatus(function(response) {
console.dir(response);
});
</script>
The above code works fine but there's a specific case when it fails. Let's assume I have two tabs open in my browser: in the first tab I have my app open, in the second one - I'm logged into Facebook. Two scenarios can take place:
I log out of Facebook and refresh the tab with my app. The result is correct:
FacebookSession is NULL
response.status from FB.getLoginStatus is 'unknown'. The user is not
logged in.
I go to the second tab, log back into Facebook and refresh the first tab with my app. The result is incorrect, but only on the first refresh:
FacebookSession is still NULL, even if
response.status of FB.getLoginStatus is 'connected'
The reason behind this fail on first refresh seems to be obvious: In the moment of reloading the page PHP SDK is triggered before Facebook cookie is refreshed. However, it's never a problem when the user logs out - in this case, somehow FacebookSession is updated instantly, as expected.
How come it does not work the same when the user logs into Facebook?

Answer 1

Does this help?
Subsequent calls to FB.getLoginStatus will return data from this cached response. This can cause problems where the user has logged into (or out of) Facebook since the last full session lookup, or if the user has removed your application in their account settings.
To get around this, you call FB.getLoginStatus with the second parameter set to true to force a roundtrip to Facebook - effectively refreshing the cache of the response object.
FB.getLoginStatus(function(response) {
// this will be called when the roundtrip to Facebook has completed
}, true);
Source: https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus
Section: Roundtrips to Facebook's servers