two facebook canvas apps, one user, two different user ids. Why? - facebook

Question

I have created 2 facebook apps, hosted in the same external domain. I have installed these two apps in a facebook page of mine and in both apps i am running the following php code at the beginning:
session_start();
// added in v4.0.0
require_once 'autoload.php';
use Facebook\FacebookSession;
use Facebook\FacebookRedirectLoginHelper;
use Facebook\FacebookRequest;
use Facebook\FacebookResponse;
use Facebook\FacebookSDKException;
use Facebook\FacebookRequestException;
use Facebook\FacebookAuthorizationException;
use Facebook\GraphObject;
use Facebook\Entities\AccessToken;
use Facebook\HttpClients\FacebookCurlHttpClient;
use Facebook\HttpClients\FacebookHttpable;
// start session
// init app with app id and secret
FacebookSession::setDefaultApplication( 'xxx','yyy' );
// login helper with redirect_uri
$helper = new FacebookRedirectLoginHelper('https://apps.facebook.com/my_namespace/' );
try
{
$session = $helper->getSessionFromRedirect();
}
catch( FacebookRequestException $ex )
{
// When Facebook returns an error
}
catch( Exception $ex )
{
// When validation fails or other local issues
}
// see if we have a session
if ( isset( $session ) )
{
// graph api request for user data
$request = new FacebookRequest( $session, 'GET', '/me' );
$response = $request->execute();
// get response
$graphObject = $response->getGraphObject();
// print data
echo '<pre>' . print_r( $graphObject, 1 ) . '</pre>';
}
else
{
// show login url
echo 'Login';
}
When I run each application, the user identity that is shownn is equal for all properties except for user id:
One app 1, i see:
Facebook\GraphObject Object
(
[backingData:protected] => Array
(
[id] => 1400416826952138
[email] => my_name#gmail.com
[first_name] => Name
[gender] => female
Etc
On app 2 I see:
Facebook\GraphObject Object
(
[backingData:protected] => Array
(
[id] => 1397126750614479
[email] => my_name#gmail.com
[first_name] => Name
[gender] => female
Etc
As i am using the same user (my account) in both apps, why are there 2 different ID for the same user account?
Thanks
Nat