选中“通知”复选框时显示通知的代码片段，并在管理中的更新和发布帖子或页面中显示消息

 function cabtv_add_post_options()
    {
        // Add our meta box for the "post" post type (default)    
        $post_types = array("post", "page");

        foreach ($post_types  as $post_type) {

            add_meta_box(\'cabtv_notif_on_post\',\'Notifications\',\'cabtv_notif_on_post_html_view\',$post_type,\'side\',\'high\');
        }

    }
    add_action(\'add_meta_boxes\', \'cabtv_add_post_options\');


    function cabtv_notif_on_post_html_view($post)
    {   
        wp_nonce_field( \'cabtv_notif_metabox\', \'cabtv_notif_metabox\' );

        $checked = get_post_meta( $post->ID, \'cabtv_notifications_sent\', true);
        $check = $checked?\'checked\':\'\';

        if ($checked) { ?>
            <div style=\'padding:10px;\'>
                <span style=\'color:red; font-weight:bold;\'>Notifications have already been sent for this post.</span>
            </div>
        <?php } ?>

        <input type="hidden" name="cabtv_meta_box_present" value="true"></input>
        <input type="checkbox" name="cabtv_send_notification" value="true" <?php echo $check; ?>></input>
        <label>
        <?php echo esc_attr(\'Send notification on \'.($post->post_status === \'publish\' ? \'update\' : \'publish\') ); ?>
        </label>

    <?php
    }




    function save_notice_meta_box_data( $post_id ) {

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

        // Verify that the nonce is valid.
        if ( ! wp_verify_nonce( $_POST[\'cabtv_notif_metabox\'], \'cabtv_notif_metabox\' ) ) {
            return;
        }

        // 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;
        }

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

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

        }
        else {

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

        /* OK, it\'s safe for us to save the data now. */

        // Make sure that it is set.
        if ( ! isset( $_POST[\'cabtv_send_notification\'] ) ) {
            return;
        }

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

        // Update the meta field in the database.
        update_post_meta( $post_id, \'cabtv_notifications_sent\', $my_data?$my_data:\'\');
    }

    add_action( \'save_post\', \'save_notice_meta_box_data\' );

**save\\u notice\\u meta\\u box\\u数据函数代码解释：**

//检查我们的nonce是否已设置。

if ( ! isset( $_POST[\'cabtv_notif_metabox\'] ) ) {
    return;
}

//检查用户的权限。

if ( isset( $_POST[\'post_type\'] ) && \'page\' == $_POST[\'post_type\'] ) {

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

    }
    else {

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

//确保已设置。

if ( ! isset( $_POST[\'cabtv_send_notification\'] ) ) {
        return;
    }

//更新数据库中的元字段。

 update_post_meta( $post_id, \'cabtv_notifications_sent\',$my_data);

//保存帖子和页面挂钩

add_action( \'save_post\', \'save_notice_meta_box_data\' );