In case your website, built with Symfony2, is using multiple databases, you must setup as much connections and Entity Managers as databases.

An Entity Manager is simply an interface that speaks to the database.

In order to illustrate my example, I will be using two databases: site and forum.

Set up the connections in config.yml

doctrine:
  dbal:
    default_connection: site # specify the connexion used by default
    connections:
      site:
        driver:   %database_driver%
        host:     %database_host%
        port:     %database_port%
        dbname:   site
        user:     site_usr
        password: site_pwd
        charset:  UTF8
      forum:
        driver:   %database_driver%
        host:     %database_host%
        port:     %database_port%
        dbname:   forum
        user:     forum_usr
        password: forum_pwd
        charset:  UTF8

Set up EM, in the same file

To begin with, disable auto-mapping, so you will be able to choose which EM is going to manage which bundle’s entities.

doctrine:
  orm:
    auto_mapping: false

Note: If there’s an error bounded with this line, just delete it.

Then, right below, set up EM while specifying mappings to each bundle.

doctrine:
  orm:
    auto_mapping: false
    default_entity_manager: web # specify the EM used by default (when using console commands f.e)

    entity_managers:
      web:
        connection: web
        mappings:
          DinduksFooBundle : ~
          DinduksBarBundle : ~
          FOSUserBundle: ~
      forum:
        connection: forum
        mappings:
          DinduksForumBundle : ~

Simply put, mappings connect and constitute the bridge between an EM and the entities of a specific bundle. In other terms, mappings call up an EM X when wanting to manipulate an entity Y.

Warning: Always make sure you map your fresh-created bundles to an EM, otherwise a “non-existent bundle” error will occur when using the doctrine:generate:entities command.

Use

In the same way you call your default EM, call the EM you need by passing its name to the getEntityManager() function.

$forumEm = $this->get('doctrine')->getEntityManager('forum');

I hope you’ll find this tutorial useful. :)

Translated from my french post Symfony2: Utiliser plusieurs bases de données