<?php
session_start();

//included file and use

$app_id = 'xxx';
$app_secret = 'xxx';
FacebookSession::setDefaultApplication($app_id, $app_secret);
$helper = new FacebookRedirectLoginHelper("`http://example/facebook4.0`/", $app_id, $app_secret);
try
{
    $session = $helper->getSessionFromRedirect();
}
catch(FacebookRequestException $ex) { }
catch(Exception $ex) { }

$loggedIn = false;

if (isset($session))
{
    if ($session)
        {
            $loggedIn = true;
            try {                     //logged here and get data
                $user_profile = (new FacebookRequest(
                $session, 'GET', '/me'
                ))->execute()->getGraphObject(GraphUser::className());

               print_r($user_profile); //print data

                }
                catch(FacebookRequestException $e)
                {
                    echo "Exception occured, code: " . $e->getCode();
                    echo " with message: " . $e->getMessage();
                }
        }
}

if(!$loggedIn)  //if user is not online // get link and add scope
{
    $loginUrl = $helper->getLoginUrl(array('public_profile','email'));
    echo "<a href='$loginUrl'>Login With Facebook</a>";
}
else
{
    print_r($user_profile); //logout link is generated here
    echo '<br><br><a href="index.php">Logout</a>'; //print to sceen

}