API page: https://api.drupal.org/api/drupal/core%21includes%21bootstrap.inc/functi...
Enter a descriptive title (above) relating to function drupal_bootstrap, then describe the problem you have found:
It appears that the docs for parameter $phase are missing DRUPAL_BOOTSTRAP_KERNEL. This is documented here: https://api.drupal.org/api/drupal/core!includes!bootstrap.inc/constant/DRUPAL_BOOTSTRAP_KERNEL/8
This information needs to be added to the drupal_bootstrap() docs.