admin_notices ON save_post

Did you ever get this working? I want to do something similar

In the interest of helpfulness, here’s one solution to the problem above. The reason why it doesn’t work the way you expect is because wordpress is issuing a redirect between the time the save_post action is called and the time the admin_notices action is called. So the action you’ve attached to admin_notices does not exist at the time that action is actually called.

In order to work around this, you can store the message temporarily during save_post and then retrieve it after the redirect. Modifying your pseudocode example from above:

add_action('save_post', 'functionx'); // called before the redirect
add_action('admin_head-post.php', 'add_plugin_notice'); // called after the redirect

function add_plugin_notice() {
  if (get_option('display_my_admin_message')) { // check whether to display the message
    add_action('admin_notices' , create_function( '', "echo '" . get_option('my_admin_message') . "';" ) );
    update_option('display_my_admin_message', 0); // turn off the message
  }
}

// essentially the same as your original functionx, except the message is stored and activated for display
function functionx () {
	if (functionA()) {
	  update_option('my_admin_message', 'Function A Returned 1.');
	} else {
	  update_option('my_admin_message', 'Function A Returned 0.');
	}
	update_option('display_my_admin_message', 1); // turn on the message
}

function functionA () {
	return (rand(1, 2) % 2); // dummy function - randomly return true or false
}

Note that this example uses the specific action admin_head-post.php after the redirect – this will prevent the add_plugin_notice function from even being added to admin_notices unless you’re looking at edit.php. If you were writing a notice to appear on another page, you would need to modify the action name to refer to that page, or use this generic one instead:

add_action('admin_head', 'add_plugin_notice');

(Also, if you’re unfamiliar with get_option and update_option, have a look at the documentation for update_option.)