how to create custom taxonomy drop downs for parents and child

Question

Can someone help me please, i'm not good with php. i have created a custom post type called "used-car" and a custom taxnomy called "used-car-category" in functions.php

Question:

I need to create a dropdown search form which displays a list of category and subcategory on homepage. example

dropdown 1 [car make] "category"
dropdown 2 [car model] "subcatagory"
Search button

when you select a car model in the dropdown eg audi, second dropdown will display the different model variant of audi.

catagory on the cms looks somthing like this:

audi < catagory
- a1 < subcatagory
- a6 < subcatagory
mercedes < catagory
- a class < subcatagory
- b class < subcatagory
- c class < subcatagory

i would like this search form to be displayed on homepage. can someone help me please? a working code would be helpful.

Thanks

Answer 1

<?php if ( is_taxonomy_hierarchical($taxonomy) ) : ?>
        <tr class="form-field term-parent-wrap">
            <th scope="row"><label for="parent"><?php _ex( 'Parent', 'term parent' ); ?></label></th>
            <td>
                <?php
                $dropdown_args = array(
                    'hide_empty'       => 0,
                    'hide_if_empty'    => false,
                    'taxonomy'         => $taxonomy,
                    'name'             => 'parent',
                    'orderby'          => 'name',
                    'selected'         => $tag->parent,
                    'exclude_tree'     => $tag->term_id,
                    'hierarchical'     => true,
                    'show_option_none' => __( 'None' ),
                );

                /** This filter is documented in wp-admin/edit-tags.php */
                $dropdown_args = apply_filters( 'taxonomy_parent_dropdown_args', $dropdown_args, $taxonomy, 'edit' );
                wp_dropdown_categories( $dropdown_args ); ?>
                <?php if ( 'category' == $taxonomy ) : ?>
                <p class="description"><?php _e('Categories, unlike tags, can have a hierarchy. You might have a Jazz category, and under that have children categories for Bebop and Big Band. Totally optional.'); ?></p>
                <?php endif; ?>
            </td>
        </tr>
<?php endif; // is_taxonomy_hierarchical() ?>