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WordPress Primary Category

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WordPress Primary Category

Set a primary category for your (custom) posts and query them in your template using native WordPress queries.

This plugin has been coded as part of a hiring interview. Now that the interview is out of the way, here’s the plugin in all its glory. It’s also hosted on GitHub.


  • Custom post types use the native category taxonomy – 'taxonomies' => array('category')

Further improvements

  • Dynamically show/hide _builtin post types (default to show).
  • Dynamically show/hide non-public (non-publicly queryable) post types (default to hide).
  • Add better communication between the Primary Category metabox and the Category metabox (anchor links or JavaScript appending).
  • Add more contextual help to both the metabox and the plugin’s settings.
  • Add/extend functionality to allow for primary taxonomies by getting all taxonomies attached to a custom post and adding the same functionality as for categories.
  • Migrate jQuery code to native JavaScript for zero-dependencies (even if jQuery is loaded by default in the post editing screen).


Depending on the publisher’s implementation and use of Yoast SEO plugin (which already has this functionality), a query can be built using the plugin’s code without adding any metaboxes or custom plugin settings. For this plugin, though, I have created the solution 100% from scratch.

Compatibility and security

  • The plugin does not use the new PHP 7 array notation, in order to be backwards compatible with older PHP versions (note the PHP requirement in the readme.txt header).
  • The plugin is translation-ready (WordPress plugin repository) by using the same name for the plugin folder, the main plugin file and the text domain.
  • The plugin is licensed as GPLv3.
  • The plugin is not accessible directly by browsing the plugin’s directory.

Photo by Sanwal Deen on Unsplash.

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