Access Drupal functions and session from a PHP script in a site subdirectory

If you want to use Drupal sessions and the logged in user object from a straight PHP script not at Drupal root but somewhere in subdirectories in a site, you will probably need to do something like I endend up doing in profiles/scf/switch.php to impersonate the Drupal site root directory.

In fact, I think the partial installation profile idea might need something like this.

(Skip down to resolution.)

Some test output code used to figure out what the domains and sessions were doing:

<?php
// global $user;
// print var_export($user,TRUE);
global $cookie_domain;
// print $cookie_domain;
print '?' . $session_name . '!!';
print session_name();
print 'cookie!!!' . $_COOKIE[session_name()]; // $cookie_domain;
?>

We started out trying minimal... it didn't stay that way.

<?php
/*
  // Minimum load of components.
  drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);
//  require_once './includes/file.inc';
  include_once './includes/module.inc';
  drupal_load('module', 'system');
*/

/*
require_once './includes/install.inc';
require_once './includes/file.inc';
require_once './modules/system/system.install';

// Load module basics.
include_once './includes/module.inc';
$module_list['system']['filename'] = 'modules/system/system.module';
$module_list['filter']['filename'] = 'modules/filter/filter.module';
module_list(TRUE, FALSE, FALSE, $module_list);
drupal_load('module', 'system');
drupal_load('module', 'filter');
*/
?>

Resolution

<?php
/**
* In which we jump through some hoops to make Drupal treat
* profiles/scf/switch.php just like the root-level index.php or update.php
*/
// remove '/profiles/scf' from current working directory and set our directory
$base_dir = substr(getcwd(), 0, -13);
chdir($base_dir);
// ini_set('include_path', '.:' . $base_dir); - use of ./ makes this not work
global $base_url;
// duplicated from bootstrap.inc conf_init().
    // Create base URL
    $base_root = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') ? 'https' : 'http';

    // As $_SERVER['HTTP_HOST'] is user input, ensure it only contains
    // characters allowed in hostnames.
    $base_url = $base_root .= '://'. preg_replace('/[^a-z0-9-:._]/i', '', $_SERVER['HTTP_HOST']);

    // $_SERVER['SCRIPT_NAME'] can, in contrast to $_SERVER['PHP_SELF'], not
    // be modified by a visitor.
    if ($dir = trim(dirname($_SERVER['SCRIPT_NAME']), '\,/')) {
      $base_path = "/$dir";
      $base_url .= $base_path;
    }
$base_url = substr($base_url, 0, -13);

require_once './includes/bootstrap.inc';

// we need the $user variable, theming...  i think we have to go all the way
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL); // DRUPAL_BOOTSTRAP_CONFIGURATION

drupal_maintenance_theme();
?>