php - How can i get all values of particular attribute in woocommerce, It shows invalid_taxonomy in WP_ERROR_OBJECT -

i m new in wordpress, set e-book store of woocommerce, want add custom shortcode in woocommerce plugin fetch list of publishers , display alphabatically. publisher custom attribute of simple product. did

$shortcodes = array(         'product'                    => __class__ . '::product',         'product_page'               => __class__ . '::product_page',         'product_category'           => __class__ . '::product_category',         'product_categories'         => __class__ . '::product_categories',         'add_to_cart'                => __class__ . '::product_add_to_cart',         'add_to_cart_url'            => __class__ . '::product_add_to_cart_url',         'products'                   => __class__ . '::products',         'recent_products'            => __class__ . '::recent_products',         'sale_products'              => __class__ . '::sale_products',         'best_selling_products'      => __class__ . '::best_selling_products',         'top_rated_products'         => __class__ . '::top_rated_products',         'featured_products'          => __class__ . '::featured_products',         'product_attribute'          => __class__ . '::product_attribute',         'related_products'           => __class__ . '::related_products',         'shop_messages'              => __class__ . '::shop_messages',         'woocommerce_order_tracking' => __class__ . '::order_tracking',         'woocommerce_cart'           => __class__ . '::cart',         'woocommerce_checkout'       => __class__ . '::checkout',         'woocommerce_my_account'     => __class__ . '::my_account',         'woocommerce_publishers'     => __class__ . '::publishers',     ); 

publisher function

public static function publishers(){ $args = array( 'posts_per_page' => 3,'posts_type' =>'product','post_status' =>'publish'); $lastposts = get_posts( $args ); foreach ( $lastposts $post ) :setup_postdata( $post );  $prod_id = get_the_id();     $terms = get_the_terms($prod_id, 'pa_publisher' );     print_r($terms); endforeach;  wp_reset_postdata(); } } 

after m not getting results, want know how publisher names in alphabetic order. after execute above code returns error

wp_error object ( [errors] => array ( [invalid_taxonomy] => array ( [0] => invalid taxonomy ) ) [error_data] => array ( ) ) 

help me plzz.. in advance