how to bootstrap or initialize joomla environment in external script

If you want to get the information about the logged in joomla user in your external script here is the recipe for it:

1. First you need to get the joomla base path eg: http://example.com
So something like below might work or you will have to adjust according to the path of your script file

$joomlaBase = dirname(__FILE__);

define( ‘_JEXEC’, 1 );
define(‘JPATH_BASE’, $joomlaBase);
define( ‘DS’, DIRECTORY_SEPARATOR );
require_once ( JPATH_BASE .DS.’includes’.DS.’defines.php’ );
require_once ( JPATH_BASE .DS.’includes’.DS.’framework.php’ );

$mainframe =& JFactory::getApplication(‘administrator’);
$mainframe->initialise();

That’s it joomla environment is initialize in your script.

So now for checking logged in user.

 if  (JFactory::getUser()->id == 0) {
// this means user is not logged in
}

After lot of trial and error above solution worked for me. I have tested in joomla 2.5.6 / 1.6
I got the reference from http://forum.joomla.org/viewtopic.php?f=304&t=580193