Question

so I’m using the Facebook PHP SDK for authenticating my user….

and I’m trying to logout my user using the destroySession() method in base_facebook.php

These are some relevant excerpts in the PHP SDK’s base_facebook.php: https://github.com/facebook/php-sdk/blob/master/src/base_facebook.php

      public function destroySession() {
        $this->setAccessToken(null);
        $this->user = 0;
        $this->clearAllPersistentData();
      }

  protected function clearAllPersistentData() {
    foreach (self::$kSupportedKeys as $key) {
      $this->clearPersistentData($key);
    }
  }

  protected function clearPersistentData($key) {
    if (!in_array($key, self::$kSupportedKeys)) {
      self::errorLog('Unsupported key passed to clearPersistentData.');
      return;
    }

    $session_var_name = $this->constructSessionVariableName($key);
    unset($_SESSION[$session_var_name]);
  }

but everytime I try to do so, Zend Framework would complain

Fatal error: Uncaught exception 'Zend_Session_Exception' with message 'session has already been started by session.auto-start or session_start()' 

Zend_Session_Exception: session has already been started by session.auto-start or session_start() 

How do I go about clearing my facebook session without triggering all these errors?

Answer 1

The prerequisite for using Zend_Session is the session must not be initiated yet. Facebook initiates it. As a solution, call session_write_close() before using Zend_Session.

Alternatively, call session_destroy() to logout the facebook user. It destroys all of the data associated with the current session.