MB Relationships is a WordPress plugin that helps you create many-to-many relationships between posts, pages, custom post types, terms, and users. The plugin is lightweight and optimized for database and query performance.

The plugin allows you to create connections from posts to posts, posts to users, and so on. Then you can perform corresponding queries to retrieve posts (or terms, users) that are connected to or from given posts (terms, users).

The plugin also supports reciprocal and bi-directional relationships.

Why Do You Need Posts To Posts Relationships In WordPress?

Post relationships are a missing part in WordPress. The only “built-in” way that mimics the post relationship in WordPress is  post_parent for pages where you can create many child pages of a page (a one-to-many relationship). Unfortunately, that’s available for pages and hierarchical post types only. Besides, it’s not a many-to-many relationship.

Below are some examples of posts relationships that might help you see the benefit of this feature:

Creating Related Posts In WordPress

The simplest example is to manually create related posts on your WordPress website. When you edit a post, you can select posts that have similar or related content and display them in the frontend for further reading.

You can also query backward: displaying posts that link to the being read post as a reference to provide more information to your readers. With this, you don’t need a WordPress-related posts plugin anymore.

Example: Events And Bands

Suppose you have two custom post types, event, and band, where:

  • In each event there may be multiple bands, and
  • Each band can participate in many events.

The relationship is described in this diagram:

Many-to-many relationships

If people want to buy tickets, they could search for events in their location and see what bands are playing on a given date, or they could search for bands they like and see what date they are playing near their location.

In this example, we have created many-to-many relationships between events and bands.

Creating Relationship Between Posts and Terms, Users

In addition to connecting between custom post types, you can use the plugin with MB Term Meta and MB User Meta to connect posts to terms, posts to users, and vice versa.

Then you can create a lot of relationships that fit your needs, for example:

  • Connect products (custom post type) and distributors (user), where each product can be distributed by multiple distributors and each distributor can distribute multiple products.
  • Connect singers (user) and songs (custom post type), where each singer can sing many songs and each song can be sung by many singers.

Bi-directional relationships

MB Relationships allows you to create bi-directional connections. You will be able to query back and forth without any problem.

The data is stored in the database as a pair of (from_id, to_id), thus making it independent from either side.

Besides, for each side, there’s a meta box that shows what is connected from/to. So you don’t have to worry about the direction of the connection anymore.

If you have built relationships with field post or taxonomy_advanced, you will see the difference here. The old way is clearly just a one-directional relationship from an object type to another. It will be so hard to query or store the items that connect to a specific post.

Plugin features

Inherit the strengths of both Meta Box and Posts 2 Posts, MB Relationship is lightweight and has a flexible API.

  • Simple APIs: the plugin provides simple APIs for registering relationships and retrieving connected items. It integrates with existing WordPress APIs such as WP_Query,get_terms and get_users.
  • Uses custom relationship table to store relationships. That helps optimize the database storage and query performance.
  • You can create relationships between any kind of content in WordPress: posts to posts, posts to users, etc.
  • Supports creating reciprocal relationships (posts-posts, users-users, …).
  • Supports creating bi-directional relationships and easily query them.
  • Display connected items easily with the shortcode.
  • Extremely lightweight and fast.
Looking for more details? Check out the plugin documentation.