config.yml

# Doctrine Configuration
doctrine:
    dbal:
        driver:   pdo_mysql
        host:     "%database_host%"
        port:     "%database_port%"
        dbname:   "%database_name%"
        user:     "%database_user%"
        password: "%database_password%"

parameters.yml

parameters:
    database_host: localhost
    database_port: null
    database_name: my_db
    database_user: root
    database_password: root