回答您的第一个问题post meta »bookauthor«这种方式将呼应/显示这一点。如果定义变量$id 在您的代码中，或者您可以按如下所示执行。

代码应该回答您的第二个问题，即如何通过挂钩将第二个标题行插入产品页woocommerce_single_product_summary. 只需添加以下额外信息：

    function wpse116660_wc_add_2nd_title() {
        ?>
        <div class="2nd-tile">
            <?php echo get_post_meta(get_the_ID(), "bookauthor", true); ?>
        </div>
        <?php
    }
    add_action( \'woocommerce_single_product_summary\', \'wpse116660_wc_add_2nd_title\', 6 );

为了更好地使用自定义的post meta，您可以按照@pl4g4和@brasofilo的建议，在产品编辑屏幕上添加一个metabox，但这当然不是必需的，您似乎知道如何使用标准的wordpresscustom fields metabox.

您可以这样添加元框，代码基于add_meta_box wordpress codex页面。

/**
 * Adds a box to the main column on the Post and Page edit screens.
 */
function wpse116660_wc_2nd_title_mb() {

    $screen = array( \'product\' );

        add_meta_box(
            \'wc_2nd_title_mb\',
            __( \'2nd title\', \'your_textdomain\' ),
            \'wc_2nd_title_inner_mb\',
            $screen,
            \'advanced\',
            \'high\'
        );
}
add_action( \'add_meta_boxes\', \'wpse116660_wc_2nd_title_mb\', 0 );

/**
 * Prints the box content.
 * 
 * @param WP_Post $post The object for the current post/page.
 */
function wpse116660_wc_2nd_title_inner_mb( $post ) {

  // Add an nonce field so we can check for it later.
  wp_nonce_field( \'wc_2nd_title_inner_mb\', \'wc_2nd_title_inner_mb_nonce\' );

  /*
   * Use get_post_meta() to retrieve an existing value
   * from the database and use the value for the form.
   */
  $value = get_post_meta( $post->ID, \'bookauthor\', true );

  echo \'<label for="bookauthor_field">\';
       _e( "Bookauthor", \'your_textdomain\' );
  echo \'</label> \';
  echo \'<input type="text" id="bookauthor_field" name="bookauthor_field" value="\' . esc_attr( $value ) . \'" size="50" />\';

}

/**
 * When the post is saved, saves our custom data.
 *
 * @param int $post_id The ID of the post being saved.
 */
function wpse116660_wc_2nd_title_save_postdata( $post_id ) {

  /*
   * We need to verify this came from the our screen and with proper authorization,
   * because save_post can be triggered at other times.
   */

  // Check if our nonce is set.
  if ( ! isset( $_POST[\'wc_2nd_title_inner_mb_nonce\'] ) )
    return $post_id;

  $nonce = $_POST[\'wc_2nd_title_inner_mb_nonce\'];

  // Verify that the nonce is valid.
  if ( ! wp_verify_nonce( $nonce, \'wc_2nd_title_inner_mb\' ) )
      return $post_id;

  // If this is an autosave, our form has not been submitted, so we don\'t want to do anything.
  if ( defined( \'DOING_AUTOSAVE\' ) && DOING_AUTOSAVE ) 
      return $post_id;

  // Check the user\'s permissions.
  if ( \'page\' == $_POST[\'post_type\'] ) {

    if ( ! current_user_can( \'edit_page\', $post_id ) )
        return $post_id;

  } else {

    if ( ! current_user_can( \'edit_post\', $post_id ) )
        return $post_id;
  }

  /* OK, its safe for us to save the data now. */

  // Sanitize user input.
  $mydata = sanitize_text_field( $_POST[\'bookauthor_field\'] );

  // Update the meta field in the database.
  update_post_meta( $post_id, \'bookauthor\', $mydata );
}
add_action( \'save_post\', \'wpse116660_wc_2nd_title_save_postdata\' );