Question

i am in a situation where i need to the build the tree from the child nodes i.e i have to travese from child node to the parent my question is is it possible and what is the algorithm for this?

Thanks in advance

Answer 1

I did something similar to what you’re looking for. I think this should work for you, with minor adjustments. Excuse the WordPressiness – you should be able to figure out what it’s doing, anyways.

function find_parents( $category_id ) {

    global $wpdb;

    $category = $category_id;

    while (1) {

        $parent_category = $wpdb->get_row(
            $wpdb->prepare("SELECT * FROM hierarchy WHERE id=%d", $category)
        );

        $data[] = array( id => $parent_category->id, name => $parent_category->category_name );

        if ($parent_category->parent_id == 0) {
            break;
        }

        $category = $parent_category->parent_id;

    }

    return $data;

}

This will return an array in reverse order an item or category, and each subsequent parent.

The function to go the opposite direction, from the top category down and will retrieve ALL categories, is:

function find_children( $parent_id, $data ) {

    foreach ( $data as $child ) {

        if ( $child->parent_id == $parent_id ) {
            $children[] = array(
                'attr' => array(
                    'id' => 'cat_' . $child->id,
                    'dbid' => $child->id,
                    'link_to' => $child->link_to,
                    'rel' => ( $child->link_to ? 'link' : 'default' )
                ),
                'data' => $child->category_name,
                'children' => find_children( $child->id, $data )
            );
        }

    }

    return $children;

}

Between the two of them, you’ll probably be able to cobble something together, I hope :/