WordPress | Category term filter

category_filter.php

<?php
// A filter function to remove certain terms or categories
function categories_filtered( $post_id, $term_slug ) {
    $category_objects = null;
    $categories = get_the_category( $post_id ); // Get the categories assigned to the post
    if ( ! empty( $categories ) ) {
        $category_ids = wp_list_pluck( $categories, 'term_id' ); // Convert list into array of cat IDs
        $excluded = get_category_by_slug( $term_slug ); // Get category object of term to be excluded
        $excluded_id = $excluded->term_id; // Get the ID of the excluded term
        $key = array_search( $excluded_id, $category_ids ); // Now get the array key of the excluded category
        if( $key ) {
            unset( $category_ids[$key] ); // If the key of the excluded category exists lets remove it
            $args = array(
                'include' => $category_ids,
                'exclude' => $excluded_id
            );
        } else {
            // Doesnt look like the excluded term is present in the array
            $args = array(
                'include' => $category_ids
            );
        }
        $categories = get_categories( $args );
        if ( ! empty( $categories ) ) {
            $category_objects = $categories;
        }
    }
    return $category_objects;
}
?>

WordPress category filter function

I put this together as I was frustrated with the Uncategorised category getting in the way

Hopefully the comments will help to explain what is going on.

Add the above to your theme's functions.php file and then use it like so:

$categories = categories_filtered( $post->ID, 'uncategorised' );

This will return an array of category objects the same as get_the_category would minus the excluded category. If no objects are found it will return null.

👍