3 comments

1. http://codex.wordpress.org/Function_Reference/register_post_type
   example:

       //add filter to ensure the text Book, or book, is displayed when user updates a book 
   add_filter('post_updated_messages', 'codex_book_updated_messages');
   function codex_book_updated_messages( $messages ) {
     global $post, $post_ID;
   
     $messages['book'] = array(
       0 => '', // Unused. Messages start at index 1.
       1 => sprintf( __('Book updated. <a href="%s">View book</a>'), esc_url( get_permalink($post_ID) ) ),
       2 => __('Custom field updated.'),
       3 => __('Custom field deleted.'),
       4 => __('Book updated.'),
       /* translators: %s: date and time of the revision */
       5 => isset($_GET['revision']) ? sprintf( __('Book restored to revision from %s'), wp_post_revision_title( (int) $_GET['revision'], false ) ) : false,
       6 => sprintf( __('Book published. <a href="%s">View book</a>'), esc_url( get_permalink($post_ID) ) ),
       7 => __('Book saved.'),
       8 => sprintf( __('Book submitted. <a target="_blank" href="%s">Preview book</a>'), esc_url( add_query_arg( 'preview', 'true', get_permalink($post_ID) ) ) ),
       9 => sprintf( __('Book scheduled for: <strong>%1$s</strong>. <a target="_blank" href="%2$s">Preview book</a>'),
         // translators: Publish box date format, see http://php.net/date
         date_i18n( __( 'M j, Y @ G:i' ), strtotime( $post->post_date ) ), esc_url( get_permalink($post_ID) ) ),
       10 => sprintf( __('Book draft updated. <a target="_blank" href="%s">Preview book</a>'), esc_url( add_query_arg( 'preview', 'true', get_permalink($post_ID) ) ) ),
     );
   
     return $messages;
   }
   

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2. Message Storage

   The 'message' part of the $_GET array is what is responsible for holding the actual message value as integer. This means that everything that gets passed in there, will be set as actual message. The messages itself are stored inside a global array in the Admin UI templates. It’s named $messages and has three keys per default:

   1. page
   2. post
   3. attachment

   The messages are stored as sub-arrays of the main $messages array.

   Notes:

   Some things to keep in mind (WP core v4.0.1):

   • The 0 is not in use.
   • The attachment messages currently are a hack and just have the string 'Media attachment updated.' on every key.
   • All message sub-arrays are 10 keys long

   How to add custom messages

   Use the post_updated_messages filter:

   add_filter( 'post_updated_messages', function( $messages )
   {
       $messages['post'][2] = 'My awesome custom field just updated. Congratulations!';
       return $messages;
   } );
   

   Look at ~/wp-admin/edit-form-advanced.php for which message is used for what.

   The fallback, if no post type is used, is the post post type messages array.

   Custom Post Types

   You can safely add your own set of messages via a callback on the bespoken filter. Just make sure that you use your custom post types name as key for the messages array:

   add_filter( 'post_updated_messages', function( $messages )
   {
       $messages['my_custom_post_type'][2] = 'Go, buy some milk!';
       return $messages;
   } );
   

   The callback itself probably is best hooked on

   do_action( "load-{$pagenow}" )
   

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3. Thought this might help some.

   After going through length and breadth of various sites I could only get a custom message displayed with help from this.

   https://onextrapixel.com/10-tips-for-a-deeply-customised-wordpress-admin-area/

   function frl_on_save_post($post_id, $post) {/* add warning filter when saving post */
   
       if($post->post_type == 'post') //test for something real here       
           add_filter('redirect_post_location', 'frl_custom_warning_filter');
   
   }
   add_action('save_post', 'frl_on_save_post', 2, 2);
   
   function frl_custom_warning_filter($location) { /* filter redirect location to add warning parameter*/
   
       $location = add_query_arg(array('warning'=>'my_warning'), $location);
       return $location;
   }
   
   function frl_warning_in_notice() { /* print warning message */
   
       if(!isset($_REQUEST['warning']) || empty($_REQUEST['warning']))
           return;
   
       $warnum = trim($_REQUEST['warning']);
   
       /* possible warnings codes and messages */                 
       $warnings = array(
           'my_warning' => __('This is my truly custom warning!', 'frl')
       );
   
       if(!isset($warnings[$warnum]))
           return; 
   
       echo '<div class="error message"><p><strong>';
       echo $warnings[$warnum];
       echo '</strong></p></div>';
   }       
   add_action('admin_notices', 'frl_warning_in_notice');
   

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