if (isset($_SERVER['db_name'])) {
  /**
   * The database credentials are stored in the Apache or Nginx vhost config
   * of the associated site with SetEnv (fastcgi_param in Nginx) parameters.
   * They are called here with $_SERVER environment variables to
   * prevent sensitive data from leaking to site administrators
   * with PHP access, that potentially might be of other sites in
   * Drupal's multisite set-up.
   * This is a security measure implemented by the Aegir project.
   */
  $databases['default']['default'] = array(
    'driver' => $_SERVER['db_type'],
    'database' => $_SERVER['db_name'],
    'username' => $_SERVER['db_user'],
    'password' => $_SERVER['db_passwd'],
    'host' => $_SERVER['db_host'],
    /* Drupal interprets $databases['db_port'] as a string, whereas Drush sees
     * it as an integer. To maintain consistency, we cast it to a string. This
     * should probably be fixed in Drush.
     */
    'port' => (string) $_SERVER['db_port'],
  );
  $db_url['default'] = $_SERVER['db_type'] . '://' . $_SERVER['db_user'] . ':' . $_SERVER['db_passwd'] . '@' . $_SERVER['db_host'] . ':' . $_SERVER['db_port'] . '/' . $_SERVER['db_name'];
}