WordPress: Admin notices

gistfile1.php

add_action('admin_notices', function() {
	$action = (isset($_REQUEST['action']) ? $_REQUEST['action'] : null);

	if ($action && $_REQUEST['page'] == 'mvc_events') {
		$notice = '<div class="updated"><p>';

		if ($action == 'delete') {
			$notice .= 'Successfully deleted.';
		} elseif ($action == 'cancel') {
			$notice .= 'Successfully cancelled.';
		} elseif ($action == '-1') {
			$notice .= 'You need to select an event.';
		}

		$notice .= '</p></div>';

		echo $notice;
	}
});