Drop com categorias para pagina de busca

<!--E importante criar uma categoria pai para buscar as
	 categorias desejadas nessa parte do codigo add o ID da categoria pai'child_of' => 56
 -->


<form role="search" method="get" id="searchform" class="searchform" action="<?php echo esc_url( home_url( '/' ) ); ?>">
  <div> <span>LOJA</span><br />
    <input type="text" value="<?php echo get_search_query(); ?>" name="s" id="s" />
    <br />
    <span >CATEGORIA</span> <br />
    <select>
      <option value="-1">Selecione a categoria</option>
<?php
    $categories = get_categories( array( 'child_of' => 56 ));
    foreach ( $categories as $category ) {
        printf( '<option value="%1$s">%2$s (%3$s)</option>',
            esc_attr( '' . $category->term_id ),
            esc_html( $category->cat_name ),
            esc_html( $category->category_count )
        );
    }
    ?>

    </select>
    <br />
    <input type="submit" id="searchsubmit" value="<?php echo esc_attr_x( 'Search', 'submit button' ); ?>" />
  </div>
</form>