Show categories in H3 then show sub-categories in a list

Question

Ok. I tried the code from another question:

<?php
    $subcategories = get_categories('&child_of=4&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
        echo '<ul>';
        foreach ($subcategories as $subcategory) {
        echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
     }
     echo '</ul>';
?>

But didn't worked. Since I'll display the main categories in a H3, I did in a non-dynamic way. So yeah, It will look a LOT of PHP. And also: it's not working.

<h3>Automação</h3>
                <?php
                    $subcategories = get_categories('&child_of=13&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Balanças</h3>
                <?php
                    $subcategories = get_categories('&child_of=34&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>              
                <h3>Caixas Registradoras</h3>
                <?php
                    $subcategories = get_categories('&child_of=42&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Gavetas de Dinheiro</h3>
                <?php
                    $subcategories = get_categories('&child_of=45&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Impressoras</h3>
                <?php
                    $subcategories = get_categories('&child_of=49&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Informática</h3>
                <?php
                    $subcategories = get_categories('&child_of=57&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Leitores</h3>
                <?php
                    $subcategories = get_categories('&child_of=61&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>
                <h3>Marcas</h3>
                <?php
                    $subcategories = get_categories('&child_of=70&hide_empty'); // List subcategories of category '4' (even the ones with no posts in them)
                    echo '<ul>';
                    foreach ($subcategories as $subcategory) {
                      echo sprintf('<li><a href="%s">%s</a></li>', get_category_link($subcategory->term_id), apply_filters('get_term', $subcategory->name));
                    }
                    echo '</ul>';
                ?>

There is any way to display the main category in a H3 and the sub-categories in a one-way PHP? Because I know the problems of performance and security when I place A LOT of PHP.

Example:

H3> AUTOMACAO
UL
LI> SUB-CATEGORY
LI> SUB-CATEGORY

Answer 1

I believe I got what you are looking for. Basically what I created was obtaining a list of all category IDs and filtering the parent categories in an array then going through and displaying it based on your formatting.

<?php //Get list of parent category IDs and put it inside of $parent_categories array
    $category_ids = get_all_category_ids();
    $parent_categories = array(); 
    foreach($category_ids as $cat_id) { 
        $category = get_category($cat_id);
        if ($category->parent == 0) {
            $parent_categories[] = $category->cat_ID;
        }
    }
?>
<?php //Display each parent <h3>category</h3> and <ul>subcategories</ul>
    foreach ($parent_categories as $pcat) :
        $category = get_category($pcat);
?>
        <h3><?php echo ucfirst($category->name); ?> </h3>
        <?php /*  if you want to show the full link you can use this instead
        <?php 
        $parentArgs =   array(
            'title_li'          => '',
            'include'           => $pcat
        );
        ?>
        <h3><?php wp_list_categories($parentArgs); ?></h3>

        */ ?>
        <ul>
        <?php 
            $childArgs =    array(
                'title_li'          => '',  //You could put the parent category title in here if you want
                'child_of'          =>$category->cat_ID
            );
            wp_list_categories($childArgs);
        ?>
        </ul>
<?php endforeach; ?>

---

ADDITIONAL INFORMATION REQUESTED:

You could display based on the taxonomy here is an example.

<?php //Get list of parent category IDs and put it inside of $parent_categories array
    $category_ids = get_all_category_ids();
    $parent_categories = array(); 
    foreach($category_ids as $cat_id) { 
        $category = get_category($cat_id);
        if ($category->parent == 0) {
            $parent_categories[] = $category->cat_ID;
        }
    }
?>
<?php //Display each parent <h3>category</h3> and <ul>subcategories</ul>
    foreach ($parent_categories as $pcat) :
        $category = get_category($pcat);
        if ($category->taxonomy == 'category') : //You change the 'category' to your taxonomy.
?>
            <h3><?php echo ucfirst($category->name); ?> </h3>
            <ul>
            <?php 
                $childArgs =    array(
                    'title_li'  => '',  //You could put the parent category title in here if you want
                    'child_of'  =>$category->cat_ID
                );
                wp_list_categories($childArgs);
            ?>
            </ul>
    <?php endif; ?>
<?php endforeach; ?>