How To Get Parent Category Slug of Current Post

Question

My theme has styling by category using the following code, which inserts the current category's slug as a CSS class.

<div class="CategorySpecificStyle 
    <?php $category = get_the_category(); echo $category[0]->slug; ?>">
        <?php echo $category[0]->cat_name; ?>
</div> 

Now i'm about to add a large number of new sub-categories, and it seems silly to add them all in CSS when I should be able to just select the parent category of the current post and apply styles to that.

I've been able to get the parent category's name:

$parentcat = get_cat_name($category[0]->category_parent);

But spaces (and capitalization) is an issue... And I can't seem to get the parent category's slug.

I know i'm probably missing a simple step somewhere, but any insight would be greatly appreciated.

Answer 1

You will need to use the ID value returned by $category[0]->category_parent and pass it through get_term(). Example:

$category = get_the_category(); 
$category_parent_id = $category[0]->category_parent;
if ( $category_parent_id != 0 ) {
    $category_parent = get_term( $category_parent_id, 'category' );
    $css_slug = $category_parent->slug;
} else {
    $css_slug = $category[0]->slug;
}

Answer 2

You will need to query for the parent category data. get_category is pretty much built for doing that.

$category = get_the_category(); 
$parent = get_category($category[0]->category_parent);
echo $parent->slug;

That will return the immediate parent of the category. That is given this set of categories:

• Cartoon
  • Dog
    • Scooby

The code above will return "Dog" if you give it the ID for "Scooby". If you want the topmost parent category-- "Cartoon"-- no matter how deep the nesting, use something like this:

$category = get_the_category(); 
$parent = get_ancestors($category[0]->term_id,'category');
if (empty($parent)) {
  $parent[] = array($category[0]->term_id);
}
$parent = array_pop($parent);
$parent = get_category($parent); 
if (!is_wp_error($parent)) {
  var_dump($parent);
} else {
  echo $parent->get_error_message();
}

That also has the advantage of relatively neat error handling.

Answer 3

I found most of the above did not work for Custom Post Types. So I wrote the following function.

Given the ID of the current ( child ) category, it works its way up the chain to give the parent(s) of the category. It returns an array containing url, name, slug and id of parents.

/**
 * @param $category_id
 *
 * @return array        Returns either empty array if no parents or
 *                      an array of  categories from base category[0] to parent category
 *                      The array has a sub array of ['id'] ['name'] ['slug'] ['url']
 *
 */

function get_category_parent_array( $category_id, $category_taxonomy = 'category'){

    $category_id = abs((int)$category_id);
    $category_taxonomy = sanitize_key( $category_taxonomy);
    
    // Sanity check for top parent - ( id = 0 )
    if( 0 == $category_id ){
        return array();
    }

    $child_category = get_term( $category_id, $category_taxonomy);
    if( empty($child_category)){
        return array();
    }

    $parent_category_id = $child_category->parent;
    if( 0 == $parent_category_id ){
        return array(); // We cant get category 0.
    }


    // We have checked if the parent_id is 0 but double check here for other issues causing empty parent category
    $parent_category = get_term( $parent_category_id, $category_taxonomy);
    if ( empty ( $parent_category ) ){
        return array();
    }

    // Prepare the return array
    $parent_array = array();

    $parent_array['id'] =   $parent_category_id;
    $parent_array['slug'] = esc_attr($parent_category->slug);
    $parent_array['name'] = esc_attr($parent_category->name);
    $parent_array['url'] =  esc_url(get_term_link( $parent_category));

    if ( 0 == $parent_category_id ){
        return $parent_array;
    }else{
        $new_parent = get_category_parent_array($parent_category_id, $category_taxonomy );
        if(! empty( $new_parent ) ){
            return array( $new_parent, $parent_array);
        }else{
            return $parent_array;
        }

    }

}

For example. In a tree of Home>Products>Platic-Bags>Poly-Bags>3muBags Where the child / current category is 3mu it returned the following:

array (
  0 => 
  array (
    'id' => 260,
    'slug' => 'plastic-bags',
    'name' => 'Plastic Bags',
    'url' => 'https://example.com/product_category/plastic-bags/',
  ),
  1 => 
  array (
    'id' => 261,
    'slug' => 'polybags',
    'name' => 'Polybags',
    'url' => 'https://exmapl.com/product_category/polybags/',
  ),
);

Answer 4

I like the previous answer from @s_ha_dum, but for getting the top-level category regardless of depth, I used what I consider to be a simpler solution:

$cats = get_the_category();
foreach ( $cats as $cat ) {
    if ( $cat->category_parent == 0 ) {
        return $cat->name; // ...or whatever other attribute/processing you want
    }
}
return ''; // This was from a shortcode; adjust the return value to taste

Answer 5

If it can help somebody... to get child cat or parent, depending on the 0 or 1 you put on the $category

$category = get_the_category();
$parent = get_cat_name( $category[0]->category_parent );
if( ! function_exists('get_cat_slug') )
{
    function get_cat_slug($cat_id) {
        $cat_id = (int) $cat_id;
        $category = &get_category($cat_id);
        return $category->slug;
    }
}
if ( !empty($parent) ) {
    $output .= '<H2>' . esc_html( $category[1]->name ) . '</H2>';                               
} else {
    $output .= '<H2>' . esc_html( $category[0]->name ) . '</H2';
}

Answer 6

You can simplify it like this:

  $category   = get_the_category();
  $cat_parent = $category[0]->category_parent;
  $category   = $cat_parent != 0 ? get_term($cat_parent, 'category')->slug : $category[0]->slug;

Answer 7

The following function is adapted to return the root category:

function get_root_category($category = null) {
  if (!$category) $category = get_the_category()[0];
  $ancestors = get_ancestors($category->term_id, 'category');
  if (empty($ancestors)) return $category;
  $root = get_category(array_pop($ancestors)); 
  return $root;
}

Usage: get_root_category()->slug

Answer 8

All the answers above are good except the "category_parent" now replaced with "parent" from 2018!

In 2021

$custom_tax = 'books_category'; //Custom taxonomy

//Get the terms from post ID
$terms = get_the_terms( $post->ID, $custom_tax );
$parent_id = $terms[0]->parent;

if ($parent_id != 0){
    $parent = get_term( $parent_id, $custom_tax);
    echo $parent->slug;
}

Answer 9

For Taxonomies in 2021

$capitulos = get_the_terms( $post->ID, 'capitulos' );
if ($capitulos) {
foreach($capitulos as $capitulo) { if ($capitulo->parent == 0) 
echo '<a href="' . get_term_link($capitulo->term_id) . '">' . $capitulo->name . '</a> ';}
}