How to configure multiple databases in Symfony?

To configure multiple databases in Symfony, you can follow these steps:

Define your database connections in your Symfony project's configuration file (typically config/packages/doctrine.yaml). You can define multiple database connections under the doctrine.dbal.connections key.

doctrine:
    dbal:
        default_connection: default
        connections:
            default:
                url: '%env(resolve:DATABASE_URL)%'
                driver: 'pdo_mysql'
                server_version: '5.7'
            secondary:
                url: '%env(resolve:SECONDARY_DATABASE_URL)%'
                driver: 'pdo_mysql'
                server_version: '5.7'

Create separate entity managers for each database connection in your Symfony project's configuration file (typically config/packages/doctrine.yaml). You can define multiple entity managers under the doctrine.orm.entity_managers key.

doctrine:
    orm:
        default_entity_manager: default
        entity_managers:
            default:
                connection: default
                mappings:
                    App:
                        is_bundle: false
                        type: annotation
                        dir: '%kernel.project_dir%/src/Entity'
                        prefix: 'App\Entity'
            secondary:
                connection: secondary
                mappings:
                    App:
                        is_bundle: false
                        type: annotation
                        dir: '%kernel.project_dir%/src/SecondaryEntity'
                        prefix: 'App\Entity'

Use the correct entity manager when working with entities from different databases. You can specify the entity manager to use when querying or persisting entities by using the doctrine service in your controllers or services.

$entityManager = $this->get('doctrine')->getManager('secondary');
$secondaryEntities = $entityManager->getRepository(SecondaryEntity::class)->findAll();

By following these steps, you can configure and use multiple databases in Symfony for your project.