Title: Peer Categories Author: Scott Reilly Published: June 12, 2009 Last modified: April 21, 2025 --- Search plugins ![](https://ps.w.org/peer-categories/assets/banner-772x250.png?rev=835972) ![](https://ps.w.org/peer-categories/assets/icon-128x128.png?rev=976260) # Peer Categories By [Scott Reilly](https://profiles.wordpress.org/coffee2code/) [Download](https://downloads.wordpress.org/plugin/peer-categories.2.3.1.zip) * [Details](https://srd.wordpress.org/plugins/peer-categories/#description) * [Reviews](https://srd.wordpress.org/plugins/peer-categories/#reviews) * [Installation](https://srd.wordpress.org/plugins/peer-categories/#installation) * [Development](https://srd.wordpress.org/plugins/peer-categories/#developers) [Support](https://wordpress.org/support/plugin/peer-categories/) ## Description This plugin provides a template tag which acts a modified version of WordPress’s built-in template tag, `the_category()`. `the_category()` lists all categories directly assigned to the specified post. `c2c_peer_categories()` lists those categories _PLUS_ any categories that are peer to those categories and _MINUS_ categories that are parents to other assigned categories. Peer categories are categories that all share the same category parent. For example, assume your category structure is hierarchical and looks like this: ``` Vegetables |-- Leafy | |-- Broccoli | |-- Bok Choy | |-- Celery |-- Fruiting | |-- Bell Pepper | |-- Cucumber | |-- Pumpkin |-- Podded | |-- Chickpea | |-- Lentil | |-- Soybean ``` If you directly assigned the categories “Fruiting” and “Pumpkin” to a post, `peer_categories()` would return a list that consists of: “Bell Pepper”, “Cucumber”, and “Pumpkin”. Notice that since “Fruiting” was a parent to a directly assigned category, it and its peers are not included in the list. If only “Fruiting” were selected as a category, then “Leafy”, “Fruiting”, and “Podded” would have been listed. By default, categories are listed as an HTML list. The first argument to the template tag allows you to define a custom separator, e.g. to have a simple comma-separated list of peer categories: ``. As with categories listed via `the_category()`, categories that are listed are presented as links to the respective category’s archive page. Example usage (based on preceding example): * `` Outputs something like: ``` ``` * `` Outputs something like: ``` Bell Pepper, Cucumber, Pumpkin ``` Links: [Plugin Homepage](https://coffee2code.com/wp-plugins/peer-categories/) | [Plugin Directory Page](https://wordpress.org/plugins/peer-categories/) | [GitHub](https://github.com/coffee2code/peer-categories/) | [Author Homepage](https://coffee2code.com) ### Developer Documentation Developer documentation can be found in [DEVELOPER-DOCS.md](https://github.com/coffee2code/peer-categories/blob/master/DEVELOPER-DOCS.md). That documentation covers the template tags and hooks provided by the plugin. As an overview, these are the template tags provided by the plugin: * `c2c_peer_categories()` : Outputs the peer categories. * `c2c_get_peer_categories_list()` : Returns the list of peer categories. * `c2c_get_peer_categories()` : Returns the list of peer categories for the specified post. These are the hooks provided by the plugin: * `c2c_peer_categories` _(action)_, `c2c_get_peer_categories_list`, `c2c_get_peer_categories`_( filters)_ : Allows for an alternative approach to safely invoke each of the identically named functions in such a way that if the plugin were deactivated or deleted, then your calls to the functions won’t cause errors on your site. * `c2c_peer_categories_list` _(filter)_ : Customizes the return value of the ` c2c_peer_categories_list()` function. * `c2c_get_peer_categories_omit_ancestors` _(filter)_ : Customizes the function argument indicating if ancestor categories of all directly assigned categories( even if directly assigned themselves) should be omitted from the return list of categories. ## Installation 1. Install via the built-in WordPress plugin installer. Or install the plugin code inside the plugins directory for your site (typically `/wp-content/plugins/`). 2. Activate the plugin through the ‘Plugins’ admin menu in WordPress 3. Optional: Add filters for ‘c2c_peer_categories_list’ to filter peer category listing 4. Use the template tag `` in a theme template somewhere inside “the loop” ## FAQ ### Why isn’t an assigned category for the post showing up in the ‘c2c_peer_categories()’ listing? If an assigned category is the parent for one or more other assigned categories for the post, then the category parent is not included in the listing. Only peers to the lowest-level assigned categories are considered. ### Does this plugin have unit tests? Yes. The tests are not packaged in the release .zip file or included in plugins. svn.wordpress.org, but can be found in the [plugin’s GitHub repository](https://github.com/coffee2code/peer-categories/). ## Reviews There are no reviews for this plugin. ## Contributors & Developers “Peer Categories” is open source software. The following people have contributed to this plugin. Contributors * [ Scott Reilly ](https://profiles.wordpress.org/coffee2code/) [Translate “Peer Categories” into your language.](https://translate.wordpress.org/projects/wp-plugins/peer-categories) ### Interested in development? [Browse the code](https://plugins.trac.wordpress.org/browser/peer-categories/), check out the [SVN repository](https://plugins.svn.wordpress.org/peer-categories/), or subscribe to the [development log](https://plugins.trac.wordpress.org/log/peer-categories/) by [RSS](https://plugins.trac.wordpress.org/log/peer-categories/?limit=100&mode=stop_on_copy&format=rss). ## Changelog #### 2.3.1 (2025-04-21) * Change: Note compatibility through WP 6.8+ * Change: Note compatibility through PHP 8.3+ * Change: Update copyright date (2025) * Unit tests: - Change: Explicitly define return type for overridden method #### 2.3 (2024-08-28) Highlights: This minor release prevents translations from containing unintended markup, removes unnecessary functionality within `c2c_get_peer_categories()`, notes compatibility through WP 6.6+, removes unit tests from release packaging, and updates copyright date (2024). Details: * Change: Remove behavior of `c2c_get_peer_categories()` potentially returning all top-level categories * Change: Prevent translations from containing unintended markup * Change: Add missing inline comment for translators * Change: Note compatibility through WP 6.6+ * Change: Add missing inline documentation for a filter argument * Change: Update copyright date (2024) * Change: Remove development and testing-related files from release packaging * New: Add `.gitignore` file * Unit tests: - Allow tests to run against current versions of WordPress - New: Add `composer.json` for PHPUnit Polyfill dependency - Hardening: Prevent direct web access to `bootstrap.php` - Change: In bootstrap, store path to plugin directory in a constant - Change: Prevent PHP warnings due to missing core-related generated files - New: Add tests for `c2c_peer_categories()` - New: Add tests for function invocation filters - Change: Tweak some inline comment formatting #### 2.2.1 (2023-05-20) * Change: Note compatibility through WP 6.3+ * Change: Update copyright date (2023) _Full changelog is available in [CHANGELOG.md](https://github.com/coffee2code/peer-categories/blob/master/CHANGELOG.md)._ ## Meta * Version **2.3.1** * Last updated **12 months ago** * Active installations **10+** * WordPress version ** 4.6 or higher ** * Tested up to **6.8.5** * Language * [English (US)](https://wordpress.org/plugins/peer-categories/) * Tags * [category](https://srd.wordpress.org/plugins/tags/category/)[coffee2code](https://srd.wordpress.org/plugins/tags/coffee2code/) [related posts](https://srd.wordpress.org/plugins/tags/related-posts/)[the_category](https://srd.wordpress.org/plugins/tags/the_category/) * [Advanced View](https://srd.wordpress.org/plugins/peer-categories/advanced/) ## Ratings No reviews have been submitted yet. [Your review](https://wordpress.org/support/plugin/peer-categories/reviews/#new-post) [See all reviews](https://wordpress.org/support/plugin/peer-categories/reviews/) ## Contributors * [ Scott Reilly ](https://profiles.wordpress.org/coffee2code/) ## Support Got something to say? Need help? [View support forum](https://wordpress.org/support/plugin/peer-categories/) ## Donate Would you like to support the advancement of this plugin? [ Donate to this plugin ](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=6ARCFJ9TX3522)