title: in zend, how to check by ID that a session exists?
body: <p>i am using google maps with xml data,
  the way google maps works is that it calls my server to get the xml(i have to pass it an url, i can't pass the xml to google),</p>
  
  <p>since all my pages are user/password protected, 
  i need to implement some sort of authentication for google maps, so i was thinking of passing it the current user session id(encrypted in some way) so that when google calls my script, i can check that a session with that id exists, thus google is calling me on behalf of that user</p>