List Categories of the Parent Category of the Current Category

Question

So, let's say I have this structure of categories

• I. Super Cat A
  • i. mini cat a
  • ii. mini cat b
  • iii. mini cat c
• I. Super Cat B
  • i. mini cat a
  • ii. mini cat b
  • iii. mini cat c

This code:

<?php if (get_categories('child_of='.$cat.'&hide_empty=0')) { ?>
        <div class="category-wrapper">
          <ul class="child-categories">
                    <?php wp_list_categories('show_count=0&child_of='.$cat.'&hide_empty=0&title_li='); ?>
          </ul>
        </div>
<?php   } ?>

enables if I am in Super Cat A it would list all mini cat a-c,

what I want to add, is if I go to mini cat a or mini cat b or mini cat c, it would list other subcategories of its parent category, say:

current location: mini cat b

will list: mini cat a & mini cat c

Anyone?

Thanks in advance and more power.

Answer 1

Assuming you have only two levels of categories, you could first retrieve the parent category and then list the child categories. Furthermore, calling get_children and wp_list_categories uses more resources than necessary, using only wp_list_categories would suffice. I've explained my answer in the following snippet that should behave exactly as you need it to!

$category_id = get_query_var( 'cat' ); // Get current catgory ID
$category = get_term( $category_id, 'category' ); // Fetch category term object

// Now, we check if the category has a parent
// If it has, we use that ID
// If it doesn't have a parent, it is a parent category itself and we use its own ID
$parent = $category->parent ? $category->parent : $category_id;

$args = array(
    'show_count' => false,
    'hide_empty' => false,
    'title_li' => '',
    'show_option_none' => '',
    'echo' => false
);

// Show the children of parent category
if ( $category->parent ) {
    $args['child_of'] = $category->parent;
    $args['exclude'] = $category_id; // Don't display the current category in this list
}
else {
    $args['child_of'] = $category_id;
}

// Get the category list
$categories_list = wp_list_categories( $args );

if ( $categories_list ) {
    ?>
    <div class="category-wrapper">
        <ul class="child-categories">
            <?php echo $categories_list; ?>
        </ul>
    </div>
    <?php
}