The session of the Facebook Log Account of my website still exists - php

Question

I use Facebook SDK 5 with an index.php and a profile.php(only for presentation the data). I use them for log in in my website with facebook account, but after the first time that someone logs in from my computer to his fb account I don't have the option to log in again. I automatically log in with his account. How can I delete the "past user data"? I've tried deleting the session but nothing happened.
session_start();
unset($_SESSION['facebook_access_token']);
unset($accesstoken);
if (isset($accesstoken)){
echo hi;
try
{
$fbuid = $fb->getUser();
$me = $fb->api('/me');
}
catch(FacebookApiException $e){}
}
$helper = $fb->getRedirectLoginHelper();
$permissions = ['email']; // optional
try {
if (isset($_SESSION['facebook_access_token'])) {
$accessToken = $_SESSION['facebook_access_token'];
} else {
$accessToken = $helper->getAccessToken();
}
} catch(Facebook\Exceptions\facebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
if (isset($accessToken)) {
if (isset($_SESSION['facebook_access_token'])) {
$fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
}
else {
// getting short-lived access token
$_SESSION['facebook_access_token'] = (string) $accessToken;
// OAuth 2.0 client handler
$oAuth2Client = $fb->getOAuth2Client();
// Exchanges a short-lived access token for a long-lived one
$longLivedAccessToken = $oAuth2Client->getLongLivedAccessToken($_SESSION['facebook_access_token']);
$_SESSION['facebook_access_token'] = (string) $longLivedAccessToken;
// setting default access token to be used in script
$fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
}
// redirect the user to the profile page if it has "code" GET variable
if (isset($_GET['code'])) {
echo hi3;
header('Location: profile.php');
}
// getting basic info about user
try {
$profile_request = $fb->get('/me?fields=name,first_name,last_name,email');
$requestPicture = $fb->get('/me/picture?redirect=false&height=200'); //getting user picture
$picture = $requestPicture->getGraphUser();
$profile = $profile_request->getGraphUser();
$fbid = $profile->getProperty('id'); // To Get Facebook ID
$fbfullname = $profile->getProperty('name'); // To Get Facebook full name
$fbemail = $profile->getProperty('email'); // To Get Facebook email
$fbpic = "<img src='".$picture['url']."' class='img-rounded'/>";
# save the user nformation in session variable
$_SESSION['fb_id'] = $fbid.'</br>';
$_SESSION['fb_name'] = $fbfullname.'</br>';
$_SESSION['fb_email'] = $fbemail.'</br>';
$_SESSION['fb_pic'] = $fbpic.'</br>';
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
session_destroy();
// redirecting user back to app login page
header("Location: ./");
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
} else {
// replace your website URL same as added in the developers.Facebook.com/apps e.g. if you used http instead of https and you used
$loginUrl = $helper->getLoginUrl('http://newpage.photoclub-tey.com.cy/please/', $permissions);
echo 'Log in with Facebook!';
}
unset($_SESSION);
unset($_SESSION['facebook_access_token']);
$accessToken->revokeToken();
session_destroy();
?>