Custom Taxonomy – Modify Function to Get Child Category

I am using these two functions which result in getting the top parent category of a custom taxonomy. These have been tested and work as expected.

However, now I am looking for a way to output the child category instead of the parent.

function get_term_top_most_parent( $term, $taxonomy ) {
    // Start from the current term
    $parent  = get_term( $term, $taxonomy );
    // Climb up the hierarchy until we reach a term with parent = '0'
    while ( $parent->parent != '0' ) {
        $term_id = $parent->parent;
        $parent  = get_term( $term_id, $taxonomy);
    }
    return $parent;
}

function get_top_parents( $taxonomy ) {
    // get terms for current post
    $terms = wp_get_object_terms( get_the_ID(), $taxonomy );
    $top_parent_terms = array();

    foreach ( $terms as $term ) {
        //get top level parent
        $top_parent = get_term_top_most_parent( $term, $taxonomy );
        //check if you have it in your array to only add it once
        if ( !in_array( $top_parent, $top_parent_terms ) ) {
            $top_parent_terms[] = $top_parent;
        }
    }

    // build output (the HTML is up to you)
    foreach ( $top_parent_terms as $term ) {
          //Add every term
          $output = $term->slug;
    }

    return $output;
}

Answers:

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Method 1

if it is for product categories, this function only needs the category id to know the childrens:

function cat_childs( $term_id = 0) {
  $children = get_terms( array(
        'child_of'      => $term_id,
        'taxonomy'      => 'product_cat',
        'hide_empty'    => true,
        'fields'        => 'ids',
  ));
return ( $children );
}

can be called like this:

cat_childs(1234);

because it can return more than one that we can check first using

$a = cat_childs(1234);
echo '<pre>';
print_r($a);

if it is the case, we just need to do a foreach loop to get them all.

This is my code to make a menu with them all until the 3rd generation that uses the cat_childs() function to check if there is a need to the next loop.

$cat_args = array( 'orderby' => 'name', 'order' => 'asc', 'hide_empty' => true);
$cats = get_terms( 'product_cat', $cat_args );
foreach ($cats as $key => $cat):
  if ($cat->parent == 0): ?>
    <p><a href="<?php echo get_term_link($cat) ?>"  style="color:red;"><?php echo $cat->name; ?></a></p><?php
    if (cat_childs($cat->term_id)):
      foreach ($cats as $key => $cat2):
        if ($cat2->parent == $cat->term_id): ?>
          <p><a href="<?php echo get_term_link($cat2) ?>" style="margin-left:20px;  color:blue;"><?php echo $cat2->name; ?></a></p><?php
          if (cat_childs($cat2->term_id)):
            foreach ($cats as $key => $cat3):
              if ($cat3->parent == $cat2->term_id): ?>
                <p><a href="<?php echo get_term_link($cat3) ?>" style="margin-left:40px; color:green;"><?php echo $cat3->name; ?></a></p><?php
              endif;
            endforeach;
          endif;
        endif;
      endforeach;
    endif;
  endif;
endforeach;

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0