To answer your first question, getting your post meta »bookauthor« this way will echo/display just that. If you are defining the variable $id in your code right – or you can do it like shown below.
The code should answer your second question, how to insert your second title line to the product page via the hook woocommerce_single_product_summary. Just add your extra information like this:
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 );
To have some more comfort with your custom post meta you can do what @pl4g4 and @brasofilo suggested and add a metabox to the product edit screen, but it’s not necessary of course, you seem to know how to do it with the standard wordpress custom fields metabox.
You can add your meta box like this, the code is based on the first example on the add_meta_box wordpress codex page.
/**
* 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' );