WP e-Commerce "Also bought"

/**
 * Displays products that were bought along with the product defined by $product_id.
 * This functionality will be deprecated and be provided by a plugin in a future version.
 */
function wpsc_also_bought( $product_id ) {
	global $wpdb;

	if ( get_option( 'wpsc_also_bought' ) == 0 ) {
		return '';
	}

	// To be made customiseable in a future release
	$also_bought_limit = 4;
	$element_widths = 144;
	$image_display_height = 134;
	$image_display_width = 134;

	// Filter will be used by a plugin to provide 'Also Bought' functionality when this is deprecated from core.
	// Filter is currently private and should not be used by plugin/theme devs as it may only be temporary.
	$output = apply_filters( '_wpsc_also_bought', '', $product_id );
	if ( ! empty( $output ) ) {
		return $output;
	}

	// If above filter returns output then the following is ignore and can be deprecated in future.
	$also_bought = $wpdb->get_results( $wpdb->prepare( "SELECT `" . $wpdb->posts . "`.* FROM `" . WPSC_TABLE_ALSO_BOUGHT . "`, `" . $wpdb->posts . "` WHERE `selected_product`= %d AND `" . WPSC_TABLE_ALSO_BOUGHT . "`.`associated_product` = `" . $wpdb->posts . "`.`id` AND `" . $wpdb->posts . "`.`post_status` IN('publish','protected') ORDER BY `" . WPSC_TABLE_ALSO_BOUGHT . "`.`quantity` DESC LIMIT $also_bought_limit", $product_id ), ARRAY_A );
	if ( is_array( $also_bought ) && count( $also_bought ) > 0 ) {
		$output .= '<h2 class="prodtitles wpsc_also_bought">' . __( 'Andra kunder har även beställt...', 'wpsc' ) . '</h2>';
		$output .= '<div class="wpsc_also_bought clearfix">';
		foreach ( $also_bought as $also_bought_data ) {
			$output .= '<div class="wpsc_also_bought_item" style="width: ' . $element_widths . 'px;">';
			if ( get_option( 'show_thumbnails' ) == 1 ) {
				$image_path = wpsc_the_product_thumbnail( $image_display_width, $image_display_height, $also_bought_data['ID'] );
				if ( $image_path ) {
					$output .= '<a href="' . esc_attr( get_permalink( $also_bought_data['ID'] ) ) . '" class="preview_link" rel="' . esc_attr( sanitize_html_class( get_the_title( $also_bought_data['ID'] ) ) ) . '">';
					$output .= '<img src="' . esc_attr( $image_path ) . '" id="product_image_' . $also_bought_data['ID'] . '" class="product_image" />';
					$output .= '</a>';
				} else {
					if ( get_option( 'product_image_width' ) != '' ) {
						$width_and_height = 'width="' . $image_display_height . '" height="' . $image_display_height . '" ';
					} else {
						$width_and_height = '';
					}
					$output .= '<img src="' . WPSC_CORE_THEME_URL . '/wpsc-images/noimage.png" title="' . esc_attr( get_the_title( $also_bought_data['ID'] ) ) . '" alt="' . esc_attr( get_the_title( $also_bought_data['ID'] ) ) . '" id="product_image_' . $also_bought_data['ID'] . '" class="product_image" ' . $width_and_height . '/>';
				}
			}

			$output .= '<p class="product-name"><a class="wpsc_product_name" href="' . get_permalink( $also_bought_data['ID'] ) . '">' . get_the_title( $also_bought_data['ID'] ) . '</a></p>';
			if ( ! wpsc_product_is_donation( $also_bought_data['ID'] ) ) {
				// Ideally use the wpsc_the_product_price_display() function here but needs some tweaking
				$price = get_product_meta( $also_bought_data['ID'], 'price', true );
				if ( ! empty( $special_price ) ) {
					$output .= '<span style="text-decoration: line-through;">' . wpsc_currency_display( $price ) . '</span>';
				} else {
					$output .= wpsc_currency_display( $price );
				}
			}
			$output .= '</div>';
		}
		$output .= '</div>';
	}
	return $output;
}