Fatal error: Uncaught exception 'Facebook\Exceptions\FacebookSDKException' with message 'Sessions are not active. Please make sure session_start() is at the top of your script.' in /var/www/html/assets/libs/Facebook/PersistentData/FacebookSessionPersistentDataHandler.php:50 Stack trace: #0 /var/www/html/assets/libs/Facebook/Helpers/FacebookRedirectLoginHelper.php(80): Facebook\PersistentData\FacebookSessionPersistentDataHandler->__construct() #1 /var/www/html/assets/libs/Facebook/Facebook.php(323): Facebook\Helpers\FacebookRedirectLoginHelper->__construct(Object(Facebook\Authentication\OAuth2Client), NULL, NULL, NULL) #2 /var/www/html/signup.php(8): Facebook\Facebook->getRedirectLoginHelper() #3 {main} thrown in /var/www/html/assets/libs/Facebook/PersistentData/FacebookSessionPersistentDataHandler.php on line 50