DEV Community

GAJALUXSAN
GAJALUXSAN

Posted on

Understanding Polymorphic Relationships in Laravel (with Examples)

When building modern Laravel applications, sometimes you need to associate a single model with more than one other model. Instead of duplicating relationship code, polymorphic relationships offer a clean, flexible way to handle these situations.

Let’s explore what polymorphic relationships are, how they work, and when to use them — with real-world code examples.

🔍 What is a Polymorphic Relationship?

In Eloquent ORM, a polymorphic relationship allows a model to belong to more than one other model using a single association.

Example: You want to allow both posts and videos to have comments.

Rather than create two tables (post_comments, video_comments), you can use one comments table with a polymorphic relationship.

🛠️ Setup: One-to-Many Polymorphic Relationship

Let’s build the classic example of posts and videos sharing the comments model.

1️⃣ Create Migrations 

php artisan make:model Post -m
php artisan make:model Video -m
php artisan make:model Comment -m
Enter fullscreen mode Exit fullscreen mode

posts table

Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->string('title');
    $table->timestamps();
});
Enter fullscreen mode Exit fullscreen mode

videos table

Schema::create('videos', function (Blueprint $table) {
    $table->id();
    $table->string('url');
    $table->timestamps();
});
Enter fullscreen mode Exit fullscreen mode

comments table

Schema::create('comments', function (Blueprint $table) {
    $table->id();
    $table->text('body');
    $table->morphs('commentable'); // Creates commentable_id & commentable_type
    $table->timestamps();
});
Enter fullscreen mode Exit fullscreen mode

2️⃣ Define Models and Relationships

Comment.php

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo();
    }
}
Enter fullscreen mode Exit fullscreen mode

Post.php

class Post extends Model
{
    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
}
Enter fullscreen mode Exit fullscreen mode

Video.php

class Video extends Model
{
    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
}
Enter fullscreen mode Exit fullscreen mode

3️⃣ Usage Example

Add a comment to a post

$post = Post::find(1);
$post->comments()->create([
    'body' => 'Nice article!'
]);
Enter fullscreen mode Exit fullscreen mode

Add a comment to a video

$video = Video::find(1);
$video->comments()->create([
    'body' => 'Awesome video!'
]);
Enter fullscreen mode Exit fullscreen mode

Get all comments of a post

$post->comments;
Enter fullscreen mode Exit fullscreen mode

Get the parent of a comment

$comment = Comment::find(1);
$comment->commentable; // Returns Post or Video model
Enter fullscreen mode Exit fullscreen mode

🔁 Other Polymorphic Relationships

  • ✅ One-to-One Polymorphic

Example: An Image model can belong to both User and Product.

  • ✅ Many-to-Many Polymorphic

Example: A Tag model can be attached to both Posts and Videos.

🎯 When to Use Polymorphic Relationships

Use polymorphic relationships when:

  • Multiple models share a common child (e.g., comments, likes, tags).
  • You want to avoid creating separate tables for each parent-child pair.
  • You value clean, maintainable relationships in your codebase.

🧠 Final Thoughts

Polymorphic relationships are a powerful feature of Laravel’s Eloquent ORM. They simplify complex relationships and reduce duplication in your code. If you ever find yourself wanting multiple models to share a relationship, this is the tool for the job!

Let me know if you want a deep dive into many-to-many polymorphic relationships or custom polymorphic morph maps in a future post! 🚀

Top comments (0)