sfGuard token login not working in Symfony 1

Question

I'm having issues getting sfGuard token login working with a Symfony app. The Symfony app is accessed through WordPress plugin. The WordPress plugin is bare bones which embeds a iframe with a token string in the WP control panel:

<iframe src="/app/index.php/api/authenticate/**token**" width="100%" height="100%">

This works fine on the live server. After digging through my error logs I found this:

PDO Connection Error: SQLSTATE[28000] [1045] Access denied for user 'db_user'@'localhost' (using password: YES), referer: http://****/wp-admin/admin.php?page=custom-sms.php 
PHP Fatal error: Call to a member function prepare() on a non-object in /var/www/vhosts/domain.com/sfapp/lib/vendor/symfony/lib/storage/sfPDOSessionStorage.class.php on line 162, referer: http://****/wp-admin/admin.php?page=custom-sms.php

The odd thing is though I'm able to write/connect to the database on the front-end of the site. What could be causing the app not to use the database username and password set in the database.yml config file?

The app.yml file:

all:
  security:
    #to auto-login to the SMS alert system from inside Wordpress admin
    token: **token**
    username: user@web.com

BTW, I've never used Symfony before and I inherited this site with no documentation.

Update

database.yml file:

# You can find more information about this file on the symfony website:
# http://www.symfony-project.org/reference/1_4/en/07-Databases

all:
  doctrine:
    class: sfDoctrineDatabase
    param:
      dsn:      mysql:host=localhost;dbname=db_name
      username: **username**
      password: **password**

2nd Update:

To add, I manually set the $env variable to prod for testing /web/index.php on the new server.

factories.yml file:

# You can find more information about this file on the symfony website:
# http://www.symfony-project.org/reference/1_4/en/05-Factories

prod:
  logger:
    class: sfAggregateLogger
    param:
      level: err
      loggers:
        sf_file_debug:
          class: sfFileLogger
          param:
            level: err
            file: %SF_LOG_DIR%/%SF_APP%_%SF_ENVIRONMENT%.log

staging:
  logger:
    class: sfAggregateLogger
    param:
      level: notice
      loggers:
        sf_file_debug:
          class: sfFileLogger
          param:
            level: notice
            file: %SF_LOG_DIR%/%SF_APP%_%SF_ENVIRONMENT%.log

test:
  storage:
    class: sfSessionTestStorage
    param:
      session_path: %SF_TEST_CACHE_DIR%/sessions

  response:
    class: sfWebResponse
    param:
      send_http_headers: false

  mailer:
    param:
      delivery_strategy: none

all:
  routing:
    class: sfPatternRouting
    param:
      generate_shortest_url:            true
      extra_parameters_as_query_string: true

  view_cache_manager:
    class: sfViewCacheManager
    param:
      cache_key_use_vary_headers: true
      cache_key_use_host_name:    true

Answer 1

Got it working. All credit goes to @j0k for the pointers.

During setup on the new server I was hitting some errors with the session storage, so I changed the storage class type on the [app]/config/factories.yml to sfNoStorage. Reverting back to sfPDOSessionStorage allows the token login to work.

all:
  storage:
    #http://www.designdisclosure.com/2009/11/symfony-doctrine-database-session-storage/
    class: sfPDOSessionStorage
    param:
      session_name: ugro
      database: doctrine
      db_table: session
      db_id_col: sess_id
      db_data_col: sess_data
      db_time_col: sess_time