How do you handle the relationship between a tag and its associated models using morphToMany

Database Table Structure

You need three tables:

- The taggable models' tables (e.g., `posts`, `videos`), each with their own primary keys.
- A `tags` table holding unique tags.
- A pivot table, commonly named `taggables`, with these columns:
- `tag_id` (integer): references the `tags` table.
- `taggable_id` (integer): the ID of the related model.
- `taggable_type` (string): the class name of the related model.

This structure allows any model to be tagged without creating separate pivot tables for each model type.

Defining Relationships in Models

On the Taggable Models (e.g., Post, Video)

Define a method that returns the polymorphic many-to-many relationship using `morphToMany`. For example, in the `Post` model:

php
public function tags()
{
    return $this->morphToMany(Tag::class, 'taggable');
}

Similarly, in the `Video` model:

php
public function tags()
{
    return $this->morphToMany(Tag::class, 'taggable');
}

Here, `'taggable'` is the "relationship name" that corresponds to the prefix used in the pivot table columns (`taggable_id`, `taggable_type`).

On the Tag Model

Define inverse relationships for each model that can be tagged, using `morphedByMany`. For example:

php
public function posts()
{
    return $this->morphedByMany(Post::class, 'taggable');
}

public function videos()
{
    return $this->morphedByMany(Video::class, 'taggable');
}

This allows you to retrieve all posts or videos associated with a particular tag.

Using the Relationship

- To get all tags for a post:

php
$post = Post::find(1);
foreach ($post->tags as $tag) {
    // work with each $tag
}

- To get all posts for a tag:

php
$tag = Tag::find(1);
foreach ($tag->posts as $post) {
    // work with each $post
}

- Similarly, you can access videos or other models tagged by the same tag.

Summary

- Use `morphToMany` on models that can be tagged to define the relationship to tags.
- Use `morphedByMany` on the `Tag` model for each taggable model type to define inverse relationships.
- Use a single pivot table `taggables` with `tag_id`, `taggable_id`, and `taggable_type` columns.
- This setup supports flexible tagging across multiple models without redundant tables.

These details follow Laravel's official documentation and examples for polymorphic many-to-many relationships[1][2][5][8].

Citations:
[1] https://laravel.com/docs/11.x/eloquent-relationships
[2] https://blog.logrocket.com/polymorphic-relationships-laravel/
[3] https://stackoverflow.com/questions/40817211/laravel-morph-relationship
[4] https://laraveldaily.com/post/polymorphic-relations-laravel-open-source-examples
[5] https://www.sitepoint.com/eloquents-polymorphic-relationships-explained/
[6] https://stackoverflow.com/questions/57522923/how-to-use-morphtomany
[7] https://simple-code.agency/blog/development/simplifying-many-to-many-relationships-with-laravel-polymorphic-relations
[8] https://kinsta.com/blog/laravel-relationships/