silverstripe-framework/docs/en/reference/versioned.md

Versioned

The Versioned class is a [api:DataObject] that adds versioning and staging capabilities to the objects.

Trapping the publication event

Sometimes, you'll want to do something whenever a particular kind of page is published. This example sends an email whenever a blog entry has been published.

:::php
class Page extends SiteTree {
  // ...
  public function onAfterPublish() {
    mail("sam@silverstripe.com", "Blog published", "The blog has been published");
    parent::onAfterPublish();
  }
}