BBpress Dropdown List

/**
 *  Add bbpress dropdown list of forums
 */
function prefix_bbpress_dropdown_forum_list() {
    if( ( !$prefix_bbpress_dropdown_forum_list = get_transient( 'prefix_bbpress_dropdown_forum_list' ) ) ) {
            $query = new WP_Query( array(
                'post_type'           => bbp_get_forum_post_type(),
                'post_status'         => bbp_get_public_status_id(),
                'ignore_sticky_posts' => true,
                'no_found_rows'       => true,
                'orderby'             => 'menu_order title',
                'order'               => 'ASC',
                'posts_per_page'      => -1 //Set Unlimited number of posts
            ) );

            // Bail if no posts
            if ( ! $query->have_posts() ) {
                return;
            }

            $prefix_bbpress_dropdown_forum_list = '
                <select id="select-theme" onChange="window.location.href=this.value">
                    <option value="#">' .esc_html__( 'Select a theme', 'theme-palace' ). '</option>';

                while ( $query->have_posts() ) {
                    $query->the_post();

                    $forum_permalink     = bbp_get_forum_permalink( $query->post->ID );
                    $forum_title         = bbp_get_forum_title( $query->post->ID );

                    $prefix_bbpress_dropdown_forum_list .= '
                    <option value="' . esc_url( $forum_permalink ) . '">' . $forum_title . '</option>';
                }
            $prefix_bbpress_dropdown_forum_list .= '</select>';

            set_transient( 'prefix_bbpress_dropdown_forum_list', $prefix_bbpress_dropdown_forum_list, 365 * DAY_IN_SECONDS );
        }
    echo $prefix_bbpress_dropdown_forum_list;
}