Wordpress seo silo category term-tree for sidebar

Question

I created a sidebar for the dynamic WordPress category pages.

SEO Silo:

Info about SEO Silos: What is a content silo and how does it benefit for SEO?

An imaginary company offers books, films and toys. And so the following categories are usually formed:

Company category:

* company
 ** books
 ** movies
 ** games

They have subcategories.

* company
 ** books
   *** drama
   *** comedy
 ** movies
   *** drama
   *** comedy
   *** romance
 ** games
   *** actions
   *** for kids
   *** click and point

The subcategories in turn have entries.

If I now come to the books category, only everything about books may appear in the category tree and not movies and games as well. Ideally not even the upper category, like that:

* company
 ** books
   *** drama
   ---- drama Book1
   ---- drama Book2

If I'm in the drama category for books, I dont want to see the others like comedy in the books category too.

If I'm in the Company category, its okay to see the first subcategories like:

* company
 ** books
 ** movies
 ** games

If I'm in the books category:

* company
 ** books
   *** drama
   *** comedy

Problem:

The code isn't optimized yet, because I'm just trying out a lot.

Active Category level 2 already works (apart from the indentation).

1. When calling up the second category, sometimes not all (existing) sub-categories appear.
2. Probably the smallest problem is that the categories are not indented as a list.

// Manual: https://stackoverflow.com/questions/9225920/how-to-check-which-level-category-it-is-for-wordpress
function get_the_level($id, $type = 'category') {
    return count(get_ancestors($id, $type));
}

function children_sidebar_shortcode($atts) {

    global $post;

    if (!is_category()) {
        return false;
    }

    $returnval = "";
    $category = get_queried_object();
    $category_id = $category->term_id;

    $n = 0;
    $item_cat_level = 0;

    // Active Category is level 2 and more
    if (get_the_level($category_id) >= 2) {

        $returnval .= "<h2>Active Category is level 2 and more</h2>";

        $args = array(
            'type'                     => 'post',
            'child_of'                 => 0,
            'parent'                   => '',
            'orderby'                  => 'term_group', //'name',
            'order'                    => 'ASC',
            'hide_empty'               => 0,
            'hierarchical'             => 1,
            'exclude'                  => '',
            'include'                  => '',
            'number'                   => '',
            'taxonomy'                 => 'category',
            'pad_counts'               => false
        );
    } else {

        $returnval .= "<h2>Active Category is level 1 or less</h2>";

        $args = array(

            'type'                     => 'post',
            'child_of'                 => $category_id,
            'parent'                   => '', // set here same category as you want to fetch only their 1st level category  on in depth child
            'orderby'                  => 'term_group', //'name',
            'order'                    => 'ASC',
            'hide_empty'               => 0,
            'hierarchical'             => 1,
            'exclude'                  => '',
            'include'                  => '',
            'number'                   => '',
            'taxonomy'                 => 'category',
            'pad_counts'               => false
        );
    }

    $categories = get_categories($args);

    if (count($categories) > 0) {

        // show the category description
        //$returnval .= category_description();

        $returnval .= "<ul>";
        foreach ($categories as $category) {
            $item_cat_level = get_the_level($category->term_id);

            // Active Category is level 2 and more
            if (get_the_level($category_id) >= 2) {

                if (
                    // Category is part of the parent Categories/Terms
                    cat_is_ancestor_of($category->term_id, $category_id)

                    // SubLevel Category 2
                    || $item_cat_level >= 2

                    // Active Category (same)
                    || $category->term_id === $category_id
                ) {
                    $category_link = sprintf(
                        '<a href="%1$s" alt="%2$s">%3$s</a>',
                        esc_url(get_category_link($category->term_id)),
                        esc_attr($category->name),
                        esc_html($category->name)
                    );

                    $returnval .= sprintf("<li class='cat-item cat-item-%d %s'>%s", $category_id, ($category->term_id === $category_id) ? 'current-cat-ancestor' : '', $category_link);
                }
            } else {

                if (
                    // Category is part of the parent Categories/Terms
                    //cat_is_ancestor_of($category->term_id, $category_id)

                    // SubLevel Category 2
                    //|| 
                    $item_cat_level <= 1

                    // Active Category (same)
                    //|| $category->term_id === $category_id
                ) {
                    $category_link = sprintf(
                        '<a href="%1$s" alt="%2$s">%3$s</a>',
                        esc_url(get_category_link($category->term_id)),
                        esc_attr($category->name),
                        esc_html($category->name)
                    );

                    $returnval .= sprintf("<li class='cat-item cat-item-%d %s'>%s", $category_id, ($category->term_id === $category_id) ? 'current-cat-ancestor' : '', $category_link);
                }
            }
        }
        $returnval .= "</ul>";
    }

    // Attributes
    $atts = shortcode_atts(
        array(
            'name' => '',
        ),
        $atts,
        ''
    );

    return $returnval;
}
add_shortcode('children_sidebar', 'children_sidebar_shortcode');

Answer 1

function children_sidebar_shortcode( $atts ) {
    // Do nothing if we're not on a category archive.
    if ( ! is_category() ) {
        return '';
    }

    // Parse the shortcode's parameters.
    $atts = shortcode_atts( array(
        'show_parent'  => 1,
    ), $atts );

    // Get the queried category object and ID.
    $current_cat    = get_queried_object();
    $current_cat_id = $current_cat->term_id;

    // Get the category's immediate children, if any.
    $parent_cat_id  = $current_cat_id;
    $categories     = get_categories( array(
        'parent'     => $parent_cat_id,
        'hide_empty' => 1,
    ) );

    // If none, get its siblings.
    // .. which means it's the last level.
    if ( empty( $categories ) ) {
        $parent_cat_id = $current_cat->parent;
        $categories    = get_categories( array(
            'parent'     => $parent_cat_id,
            'hide_empty' => 1,
        ) );
    }

    $heading = '';
    $list    = '<ul class="cat-list">';

    foreach ( $categories as $term ) {
        $class = 'cat-item';

        // If it's the current category, show the name only.
        if ( $current_cat_id === $term->term_id ) {
            $class .= ' current-cat';

            $cat_name = '<span>' . esc_html( $term->name ) . '</span>';
        // If it's not the current category, add a link to view the category
        // archive.
        } else {
            $cat_name = '<a href="' . esc_url( get_category_link( $term ) ) . '">' .
                esc_html( $term->name ) . '</a>';
        }

        $list .= "<li class='$class'>$cat_name</li>";
    }

    $list .= '</ul>';

    if ( $parent_cat_id && $atts['show_parent'] ) {
        $term = get_category( $parent_cat_id );

        $heading = '<h3>' . esc_html( $term->name ) . '</h3>';
    }

    return "$heading $list";
}

if you are looking for a category tree with only siblings then tis is the answer 

and if you want to have full control over html markup replace the entire forarch with this code 

$list .= wp_list_categories( array(
    'current_category' => $current_cat_id,
    'parent'           => $parent_cat_id,
    'hide_empty'       => 1,
    'title_li'         => '',
    'echo'             => 0,
) );