The SitePoint PHP blog has a tutorial posted from Andrew Cairns showing you how to model an aggregate with Eloquent, the database access layer from the Laravel framework. The "aggregate" here is an implementation of the Aggregate design pattern, a system of smaller opbjects operating as a whole.
The Aggregate pattern is an important part of Domain Driven Design. It prevents inconsistencies and is responsible for enforcing business rules within a collection of objects. For these reasons alone, it is clear to see why it is a key component of a domain model.
[...] Mixing persistence concerns into a Domain Model can become complex and lead to a lot of bad decisions. This does not mean that it is impossible to create an Active Record Domain Model. In this article, we will work through an example of building an Aggregate which also extends Eloquent: a popular Active Record ORM.
They start with a brief summary of what the Aggregate design pattern, how its objects work together and the point of a "root" object. They help illustrate how it would in a more real-world situation with a simple blog system, starting with a simple
Post object minus the Eloquent integration. From there they bring in Eloquent, showing how to extend it with the class and what features it introduces. Most of the changes they make then revolve around a "lock" on the post and where value objects and the invariant rule comes in to play.