Show parent categories and sub categories but not grand children categories

Question

I'm struggling with displaying sub categories limited to only direct children of the parent on category page... I hope someone can help me with that :)

I have working code - when the current category is selected, it displays all its subcategories... but also including grand children and so on...

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

  $parent = $category->parent ? $category->parent : 
  $category_id;

  $args = array(
     'show_count' => false,
     'hide_empty' => true,
     '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="subcategory-wrapper">
        <ul class="menu">
          <?php echo $categories_list; ?>
        </ul>
      </div>
    <?php } ?>

How to display only direct children of current parent category?

What I see now with above code:

=== Current category page selected (parent) ===

• Child 01

  • Grandchild 01

• Child 02

  • Grand child 01

    • Grand grand child 01

• Child 03

• Child 04

  • Grand child 01

What I want to see (even if the parent category has grand children):

=== Current category page selected (parent) ===

• Child 01

• Child 02

• Child 03

• Child 04

UPDATE:

to hide grand sub categories, change the $args array to:

 $args = array(
 'show_count' => false,
 'hide_empty' => true,
 'depth'=>1,
 'title_li' => '',
 'show_option_none' => '',
 'echo' => false
 );

---

Another problem is that his code doesn't work on the post pages, but only on archive/category pages.

Is there a way to get the same result - show direct children of the parent category to which the post belongs - on the post page?

This is what I have now on the post page:

• Parent category

= = = = = =

Post content here

= = = = = =

This is what I want to have on the post page ( -> I want to display direct children of parent category like the code above does...but unfortunately this code doesn't work on the post page):

• Parent category

  • Child 01 (the post belongs to this subcategory)

  • Child 02 (the post doesn't belong to this subcategory, but it is displayed, because it's the child of the parent category)

  • Child 03 (the post doesn't belong to this subcategory, but it is displayed, because it's the child of the parent category) etc.

= = = = = =

Post content here

= = = = = =

Any ideas?

Answer 1

In the single post you can get the parent category like this

$category = wp_get_object_terms(get_the_ID(), 'category', array('parent'=>0));

$args = array(
 'show_count' => false,
 'hide_empty' => true,
 'title_li' => '',
 'show_option_none' => '',
 'echo' => false,
 'depth' => 1
 );


$args['child_of'] = $category[0]->term_id;

// Get the category list
$categories_list = wp_list_categories( $args );
if ( $categories_list ) {?>
  <div class="subcategory-wrapper">
    <ul class="menu">
      <?php echo $categories_list; ?>
    </ul>
  </div>
<?php } ?>