How to retrieve all children terms of a parent terms of a custom taxonomy according to hierarchy in WordPress?

Question

I'm trying to retrieve all children terms not as an array that get_term_children() function provides, rather as hierarchy level based like a tree structure.

I've been trying with

$childTerms = get_term_children( $term->term_taxonomy_id,  $taxonomy);
    if(!empty($childTerms)): 
        foreach($childTerms as $childTerm):
            d(get_term($childTerm, $taxonomy)->name);
        endforeach;
    endif;

But, the problem is that I got all child terms of a parent term as of the same level. as follows:

string(2) "TV"
string(8) "Computer"
string(10) "Cell Phone"
string(6) "Camera"
string(27) "Security & Surveillance"
string(7) "Desktop"
string(6) "Laptop"
string(6) "Tablet"

Whereas, the desktop, laptop, tablet terms are children of parent computer term.

But, I would like to get them as follows:

string(2) "TV"
string(8) "Computer"
          string(7) "Desktop"
          string(6) "Laptop"
          string(6) "Tablet"
string(10) "Cell Phone"
string(6) "Camera"
string(27) "Security & Surveillance"

how can I get this according to hierarchy level, like that of in WordPress menu?

Answer 1

First, you have to get all parent categories, and then based on parent id you can write a recurring function that gives you the child category of given id. check below code.

function get_child_categories( $parent_category_id ){
    $html = '';
    $child_categories = get_categories( array( 'parent' => $parent_category_id, 'hide_empty' => false, 'taxonomy' => $taxonomy ) );
    if( !empty( $child_categories ) ){
        $html .= '<ul>';
        foreach ( $child_categories as $child_category ) {
            $html .= '<li class="child">'.$child_category->name;
            $html .= get_child_categories( $child_category->term_id );
            $html .= '</li>';
        }
        $html .= '</ul>';
    }
    return $html;
}

function list_categories(){
    $html = '';
    $parent_categories = get_categories( array( 'parent' => 0, 'hide_empty' => false, 'taxonomy' => $taxonomy ) );
    $html.= '<ul>';
    foreach ( $parent_categories as $parent_category ) {
        $html .= '<li class="parent">'.$parent_category->name;
        $html .= get_child_categories( $parent_category->term_id  );
        $html .= '</li>';
    }
    $html.= '</ul>';
    return $html;
}
add_shortcode( 'list_categories', 'list_categories' );

Output

• A - Main category
• • B - Child Category
• • C - Child Category
• • • D - Nested Child Category( if available )
• E - Main category
• • F - Child Category
• • G - Child Category
• • • H - Nested Child Category( if available )