Joomla 3 authentication to get access to external app in PHP

Question

I've found this very useful script to check the authentication in Joomla.

Joomla 3 External authentication script

<?php
/**
 * Joomla! External authentication script
 *
 * @author vdespa
 * Version 1.0
 *
 * Code adapted from /index.php
 *
 * @package    Joomla.Site
 *
 * @copyright  Copyright (C) 2005 - 2014 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE.txt
 */
if (version_compare(PHP_VERSION, '5.3.1', '<'))
{
    die('Your host needs to use PHP 5.3.1 or higher to run this version of Joomla!');
}
/**
 * Constant that is checked in included files to prevent direct access.
 * define() is used in the installation folder rather than "const" to not error for PHP 5.2 and lower
 */
define('_JEXEC', 1);
if (file_exists(__DIR__ . '/defines.php'))
{
    include_once __DIR__ . '/defines.php';
}
if (!defined('_JDEFINES'))
{
    define('JPATH_BASE', __DIR__);
    require_once JPATH_BASE . '/includes/defines.php';
}
require_once JPATH_BASE . '/includes/framework.php';
// Instantiate the application.
$app = JFactory::getApplication('site');
// JFactory
require_once (JPATH_BASE .'/libraries/joomla/factory.php');
// Hardcoded for now
$credentials['username'] = 'adam';
$credentials['password'] = 'adam';
/**
 * Code adapted from plugins/authentication/joomla/joomla.php
 *
 * @package     Joomla.Plugin
 * @subpackage  Authentication.joomla
 *
 * @copyright   Copyright (C) 2005 - 2014 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
// Get a database object
$db    = JFactory::getDbo();
$query = $db->getQuery(true)
    ->select('id, password')
    ->from('#__users')
    ->where('username=' . $db->quote($credentials['username']));
$db->setQuery($query);
$result = $db->loadObject();
if ($result)
{
    $match = JUserHelper::verifyPassword($credentials['password'], $result->password, $result->id);
    if ($match === true)
    {
        // Bring this in line with the rest of the system
        $user = JUser::getInstance($result->id);
        echo 'Joomla! Authentication was successful!';
    }
    else
    {
        // Invalid password
        // Prmitive error handling
        die('Invalid password');
    }
} else {
    // Invalid user
    // Prmitive error handling
    die('Cound not find user in the database');
}
?>

I'd like to use this to get the user authentication on my joomla website (domain_name/index.php) to an app in PHP I'm coding (domain_name/app/index.php) It works perfectly, but the harcoded part is a problem and I don't know how to dynamically get these variables depending on the user:

// Hardcoded for now
$credentials['username'] = 'adam';
$credentials['password'] = 'adam';

Does anyone have a hint or solution on how I can do this? Thank you in advance!

Answer 1

Finally I could get what I wanted. I kept the first half of the script :

<?php
/**
 * Joomla! External authentication script
 *
 * @author vdespa
 * Version 1.0
 *
 * Code adapted from /index.php
 *
 * @package    Joomla.Site
 *
 * @copyright  Copyright (C) 2005 - 2014 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE.txt
 */
if (version_compare(PHP_VERSION, '5.3.1', '<'))
{
    die('Your host needs to use PHP 5.3.1 or higher to run this version of Joomla!');
}
/**
 * Constant that is checked in included files to prevent direct access.
 * define() is used in the installation folder rather than "const" to not error for PHP 5.2 and lower
 */
define('_JEXEC', 1);
if (file_exists(__DIR__ . '/defines.php'))
{
    include_once __DIR__ . '/defines.php';
}
if (!defined('_JDEFINES'))
{
    define('JPATH_BASE', __DIR__);
    require_once JPATH_BASE . '/includes/defines.php';
}
require_once JPATH_BASE . '/includes/framework.php';
// Instantiate the application.
$app = JFactory::getApplication('site');
?>

and recover the user ID JFactory::getUser()->id in my app. Then I just had to create my variables from this ID $_userID = JFactory::getUser()->id.