我这里有这个代码，我不知道如何在下拉菜单中获取它。

<H3>Availabilities</H3>
<?php
$taxonomy = \'category\';

// Get the term IDs assigned to post.
$post_terms = wp_get_object_terms( $post->ID, $taxonomy, array( \'fields\' => \'ids\' ) );

// Separator between links.
$separator = \', \';

if ( ! empty( $post_terms ) && ! is_wp_error( $post_terms ) ) {

    $term_ids = implode( \',\' , $post_terms );

    $terms = wp_list_categories( array(
        \'title_li\' => \'\',
        \'style\'    => \'none\',
        \'echo\'     => false,
        \'taxonomy\' => $taxonomy,
        \'include\'  => $term_ids,
        \'child_of\' => 61,

    ) );

    $terms = rtrim( trim( str_replace( \'<br />\',  $separator, $terms ) ), $separator );

    // Display post categories.
    echo  $terms;


} ?>