How to use settings.local.php with Drupal 7?
When u install drupal u need to copy example.settings.php into settings.php, after drupal installation u need to include following code in settings.php:

if (file_exists(DRUPAL_ROOT . '/' . conf_path() . '/settings.local.php')) { include DRUPAL_ROOT . '/' . conf_path() . '/settings.local.php'; }