I have added the code to get the author, but it displays the author's ID number. How can I get the author's name to show and their gravatar.
CODE
<?php
$product_pages_args = array(
'meta_key' => '_wp_page_template',
'meta_value' => 'page_library_html_content.php',
'hierarchical' => '0'
);
$product_pages = get_pages( $product_pages_args );
?>
<?php
foreach ( $product_pages as $product_page ) {
echo '<div id="posts" class="flex_100">';
echo '<div id="library_title"><a href="' . get_permalink( $product_page->ID ) . '">' . $product_page->post_title . '</a></div>';
echo '<div class="library-content">' . get_post_field('post_content', $product_page->ID ) . '</div>';
echo '<div class="library-author">' . get_post_field('post_author', $product_page->ID ) . '</div></div>';
}
?>