How do I show child categories if in a parent category, and posts if in a child?

Question

I was hoping to do all of this within the category.php template, with help from the functions.php if needed.

If my setup is:

Parent 1
--Child 1
--Child 2
Parent 2
--Child 3
--Child 4
Parent 3
--Child 5
--Child 6

...and so on I would like to be able to do this:

If I was viewing Parent 1 (or 2/3), it would show me Child 1 and Child 2. However, I don't want to use wp_list_categories because for each Child, I would like to show a thumbnail (from a plugin function), the Child's name, and the category description.

If I was viewing Child 1 (or 2/3/4/5/6), it would show me the latest 2 posts using the standard Loop.

I would like avoiding having to do this using hard-coded contitionals with the specific names of the categories, in case new ones will be added in the future.

Any assistance will be appreciated. Thank you!

Answer 1

Solved, thanks to nofearinc on the wp.org irc chat! :)

https://gist.github.com/mpeshev/cb1cd3c56d06017b3d87

<?php 

$cat_id = get_query_var('cat');

if( ! empty( $cat_id ) ) {
    $category = get_category( $cat_id, ARRAY_A );

    if( ! empty( $category ) ) {
        // parent category
        if( $category['parent'] === '0' ) {

            // get child IDs
            $terms = get_term_children( $cat_id, 'category' );

            foreach( $terms as $term_id ) {
                $child_category = get_term( $term_id, 'category' );

                // if you need the category
                $category_name = $child_category->name;


                /**
                 * Sample data in your child category object: 
                 * 
                 * object(stdClass)[365]
                          public 'term_id' => string '14' (length=2)
                          public 'name' => string 'Child 1' (length=7)
                          public 'slug' => string 'child-1' (length=7)
                          public 'term_group' => string '0' (length=1)
                          public 'term_taxonomy_id' => string '14' (length=2)
                          public 'taxonomy' => string 'category' (length=8)
                          public 'description' => string '' (length=0)
                          public 'parent' => string '12' (length=2)
                          public 'count' => string '5' (length=1)
                          public 'object_id' => string '33' (length=2)
                 * 
                 * 
                 */

                // do whatever you like with the categories now...
            }

        } else { // in child category
            // do the regular loop here, if ( have_posts() ) ...
        }
    }
}

Answer 2

I want to say that the above answer worked for me, but I needed to make some slight adjustments to the if statement. I also made an adjustment to work like...

if the post category is a parent, display the children

if the post category is a parent but has no children, display posts

<?php 

$cat_id = get_query_var('cat');

if( ! empty( $cat_id ) ) {
    $category = get_category( $cat_id, ARRAY_A );

    if( ! empty( $category ) ) {
        //get child cats
        $terms = get_term_children( $cat_id, 'category' );
        // parent category
        if( $category['parent'] == '0' and $terms[0] != '') {

                foreach( $terms as $term_id ) {
                    $child_category = get_term( $term_id, 'category' );

                    // if you need the category
                    $category_name = $child_category->name;


                    /**
                     * Sample data in your child category object: 
                     * 
                     * object(stdClass)[365]
                              public 'term_id' => string '14' (length=2)
                              public 'name' => string 'Child 1' (length=7)
                              public 'slug' => string 'child-1' (length=7)
                              public 'term_group' => string '0' (length=1)
                              public 'term_taxonomy_id' => string '14' (length=2)
                              public 'taxonomy' => string 'category' (length=8)
                              public 'description' => string '' (length=0)
                              public 'parent' => string '12' (length=2)
                              public 'count' => string '5' (length=1)
                              public 'object_id' => string '33' (length=2)
                     * 
                     * 
                     */

                    // do whatever you like with the categories now...
                }
            }  
            else { // in child category
                // do the regular loop here, if ( have_posts() ) ...
            }
        }
    }