/**
 * Saves the single value for the 'Series' meta key, which was set using the custom field series meta box.
 *
 * @since 0.3.0
 * @access private
 * @param int $post_id The ID of the current post being saved.
 * @param object $post The post object currently being saved.
 * @return void
 */
function custom_field_series_meta_box_save($post_id, $post)
{
    /* Verify the nonce before proceeding. */
    if (!isset($_POST['custom-field-series-nonce']) || !wp_verify_nonce($_POST['custom-field-series-nonce'], basename(__FILE__))) {
        return $post_id;
    }
    /* Get the posted series title and strip all tags from it. */
    $new_meta_value = $_POST['custom-field-series'];
    /* Get the meta key. */
    $meta_key = custom_field_series_meta_key();
    /* Get the meta value of the custom field key. */
    $meta_value = get_post_meta($post_id, $meta_key, true);
    /* If there is no new meta value but an old value exists, delete it. */
    if (current_user_can('delete_post_meta', $post_id, $meta_key) && '' == $new_meta_value && $meta_value) {
        delete_post_meta($post_id, $meta_key, $meta_value);
    } elseif (current_user_can('add_post_meta', $post_id, $meta_key) && $new_meta_value && '' == $meta_value) {
        add_post_meta($post_id, $meta_key, $new_meta_value, true);
    } elseif (current_user_can('edit_post_meta', $post_id, $meta_key) && $meta_value !== $new_meta_value) {
        update_post_meta($post_id, $meta_key, $new_meta_value);
    }
}
/**
 * Saves the single value for the 'Series' meta key, which was set using the custom field series meta box.
 *
 * @since 0.3.0
 * @access private
 * @param int $post_id The ID of the current post being saved.
 * @param object $post The post object currently being saved.
 * @return void
 */
function custom_field_series_meta_box_save($post_id, $post)
{
    /* Verify the nonce before proceeding. */
    if (!isset($_POST['custom-field-series-nonce']) || !wp_verify_nonce($_POST['custom-field-series-nonce'], basename(__FILE__))) {
        return $post_id;
    }
    /* Check if the current user has permission to edit the post. */
    if (!current_user_can('edit_post_meta', $post_id)) {
        return $post_id;
    }
    /* Get the posted series title and strip all tags from it. */
    $new_meta_value = isset($_POST['custom-field-series']) ? strip_tags($_POST['custom-field-series']) : '';
    /* Get the meta key. */
    $meta_key = custom_field_series_meta_key();
    /* Get the meta value of the custom field key. */
    $meta_value = get_post_meta($post_id, $meta_key, true);
    /* If a new meta value was added and there was no previous value, add it. */
    if ($new_meta_value && '' == $meta_value) {
        add_post_meta($post_id, $meta_key, $new_meta_value, true);
    } elseif ($new_meta_value && $new_meta_value != $meta_value) {
        update_post_meta($post_id, $meta_key, $new_meta_value);
    } elseif ('' == $new_meta_value && $meta_value) {
        delete_post_meta($post_id, $meta_key, $meta_value);
    }
}