Loop parent terms {display posts} AND loop child terms {display posts}

Question

I am trying to loop through the category taxonomy and display the posts attached to each term, with a heading (the term name) separating each term's posts (and also display all the terms, even those that are not attached to any posts).

Additionally, I need the child terms to be displayed as subheadings under their parent term's heading.

For example:

• AUTOMOTIVE (top-level/parent term w/ no children)
  • Post 1
  • Post 2
• BUILDING SUPPLY (parent term)
  • Drywall (child term)
    • Post 3
    • Post 4

After hours of reading and trial & error I have this code working to display just the top-level, parent terms first. I'm hoping a Wordpress ninja can make my day and guide me where to go now:

    <?php 
        $taxonomy = 'category'; // Choose the taxonomy
        // Get all the terms
        $terms = get_terms( $taxonomy, array(
            'hide_empty' => false,) // Show terms with no posts attached
            );
        foreach ($terms as $term) { // Cycle through terms, one at a time
            // Check and see if the term is a top-level parent - if so, display it
            $parent = $term->parent;
            if ( $parent=='0' ) {
                echo '<h2>' . $term->name . '</h2>';

                 ***Need to loop term posts here, with headings for child terms***

            } 
        }
    ?>

Answer 1

You need to first filter on parent category, then after if you got a child category of any parent category, then you need to find out post of that category.

Please try below code and let me know if you have any query:

<?php 
    $terms = get_terms( array(
        'taxonomy' => 'category', //Default category
        'hide_empty' => false,                  
    ) );

    echo "<ul>";
    foreach ($terms as $term) {                     
        $parent = $term->parent;
        if ( $parent == '0' ) {
            /* Parent category */
            echo '<li>' . $term->name . '</li>';

            /* Child category */
            $childrens = get_categories( array ('parent' => $term->term_id ));
            echo "<ul>";
            foreach($childrens as $children) :                          
                $args = array(
                    'post_type' => 'post',
                    'tax_query' => array(
                        array(
                            'taxonomy' => 'category', //Default category
                            'field'    => 'slug',
                            'terms'    => $children->slug,
                        ),
                    ),
                );
                echo '<li>' . $children->name . '</li>';    
                /*  Child category posts */
                ?>                          
                <ul>
                <? 
                $loop1 = new wp_Query($args);
                while($loop1->have_posts()) : $loop1->the_post();
                    the_title( '<h6>', '</h6>' );
                endwhile;
                wp_reset_query(); 
                ?>
                </ul>
                <?php   
            endforeach;
            echo "</ul>";

            /*  Parent category posts */
            if (empty($childrens))
            {
            ?>                          
            <ul>
            <? 
            $args = array(
                'post_type' => 'post',
                'tax_query' => array(
                    array(
                        'taxonomy' => 'category',
                        'field'    => 'slug',
                        'terms'    => $term->slug,
                    ),
                ),
            );
            $loop = new wp_Query($args);
            while($loop->have_posts()) : $loop->the_post();
            the_title( '<h6>', '</h6>' );
            endwhile;
            wp_reset_query(); 
            ?>
            </ul>
            <?php
            }   
        }
    }
    echo "</ul>";
?>