SitePoint PHP Blog: Re-Introducing Eloquent’s Polymorphic Relationships

On the SitePoint PHP blog they've posted a tutorial from Christopher Vundi that looks at the relationships that are a part of the Eloquent database package in Laravel. He uses the article to re-introduce polymorphic relationships you can define between your models to make cross-entity data access easier.

You’ve probably used different types of relationships between models or database tables, like those commonly seen in Laravel: one-to-one, one-to-many, many-to-many, and has-many-through. But there’s another type of relationship that’s not so common: polymorphic. So what is a polymorphic relationship?

A polymorphic relationship is where a model can belong to more than one other model on a single association. [...] With polymorphic relationships, we don’t need two tables. Let’s look into polymorphic relationships through a practical example.

He then starts in on what he'll be making in the tutorial, a system to manage songs, albums and upvotes. He outlines the basic table structure and uses the artisan command to generate both the models and migrations for the three tables. He then runs the migration to build out the tables and starts filling in the relation methods (hasOne, belongsTo, etc) and the special "morph*" methods to define the polymorphic relationships. He includes code examples showing how to access the information from the model objects and how to create custom polymorphic types if needed.