How to Get Primary Category on WordPress Using Yoast Plugin

Displaying or get primary category on WordPress in both admin and front-end pages can be a challenge because a post could belong to several different categories and if the theme has to display multi categories for each post in a list, it could get messy. This is where a primary category comes in handy.

Yoast SEO is a great plugin for managing general SEO, it also provides a lot of features that can easily to be tweaked. If a blog post has multiple categories, and want to designate the first selected category as the “Primary Category”. here is tutorial demonstrates step by step how to get a primary category on WordPress.

Prerequisites

Before starting with this guide, make sure you have permission access to WordPress project root directory and had installed Yoast plugin

Step 1: Creating Function in Inc Directory of WP Theme

We need to create a file of function to handle selecting this primary category in inc directory and we can hook in and grab it by calling with the function

Go to WordPress root directory ➝ wp-content ➝ themes ➝ YOUR THEME NAME ➝ inc

Then create a file, for example it’s called primary-category.php and add or copy paste the following code

<?php
function get_primary_category( $post = 0 ) {
  if ( ! $post ) {
    $post = get_the_ID();
  }
  // SHOW YOAST PRIMARY CATEGORY, OR FIRST CATEGORY
  $category = get_the_category( $post );
  $primary_category = array();
  // If post has a category assigned.
  if ($category){
    $category_display = '';
    $category_slug = '';
    $category_link = '';
    $category_id = '';

    if ( class_exists('WPSEO_Primary_Term') )
    {
      // Show the post's 'Primary' category, if this Yoast feature is available, & one is set
      $wpseo_primary_term = new WPSEO_Primary_Term( 'category', get_the_id( $post ) );
      $wpseo_primary_term = $wpseo_primary_term->get_primary_term();
      $term = get_term( $wpseo_primary_term );
      if (is_wp_error($term)) {
        // Default to first category (not Yoast) if an error is returned
        $category_display = $category[0]->name;
        $category_slug = $category[0]->slug;
        $category_link = get_category_link( $category[0]->term_id );
        $category_id = $category[0]->term_id;
        
      } else {
        // Yoast Primary category
        $category_display = $term->name;
        $category_slug = $term->slug;
        $category_link = get_category_link( $term->term_id );
        $category_id = $term->term_id;
      }
    }
    else {
      // Default, display the first category in WP's list of assigned categories
      $category_display = $category[0]->name;
      $category_slug = $category[0]->slug;
      $category_link = get_category_link( $category[0]->term_id );
      $category_id = $term->term_id;
    }
    $primary_category['url'] = $category_link;
    $primary_category['slug'] = $category_slug;
    $primary_category['title'] = $category_display;
    $primary_category['id'] = $category_id;

  }
  return $primary_category;
}
?>

Now we have a function get_primary_category() for getting the primary category with return or echo to use in WordPress theme.

Step 2: Modify Functions File

A functions.php or the theme functions file is a template used by WordPress themes. We need to include primary-category.php into functions.php to get automatically loaded in both admin and front-end pages of a WordPress site.

Go to WP root directory ➝ wp-content ➝ themes ➝ YOUR THEME NAME ➝ functions.php

Then add or copy paste the following code into function.php

require get_template_directory() . '/inc/primary-category.php';

Now a function get_primary_category() can be grab in both admin and front-end pages of a WordPress site.

Step 3: Using Function in Admin or Front-end Site

To display WordPress primary categories it’s now simply call a function get_primary_category(); Let’s we test it in a single page WordPress theme

echo '<pre>'.print_r(get_primary_category(get_the_ID()), true).'</pre>';

Or

echo '<pre>'.print_r(get_primary_category(), true).'</pre>';

You will see output on the browser

Array
(
    [url] => URL...
    [slug] => Primary Category Slug......
    [title] => Primary Primary Title..... 
    [id] => Primary Categery ID
)

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