Hierarchical terms list

gistfile1.txt

/**
 * Recursively sort an array of taxonomy terms hierarchically. Child categories will be
 * placed under a 'children' member of their parent term.
 * @param Array   $cats     taxonomy term objects to sort
 * @param integer $parentId the current parent ID to put them in
 */
function sort_terms_hierarchicaly(Array $cats, $parentId = 0)
{
    $into = [];
    foreach ($cats as $i => $cat) {
        if ($cat->parent == $parentId) {
            $cat->children = sort_terms_hierarchicaly($cats, $cat->term_id);
            $into[$cat->term_id] = $cat;
        }
    }
    return $into;
}

$sorted_terms = sort_terms_hierarchicaly($terms);