Callback Demo

callback-demo.php

<?php # -*- coding: utf-8 -*-
/*
Plugin Name: Callback Demo
Description: Demonstrating how a meta box and a menu page can take the same callback function.
Version:     1.0
Required:    3.1
Author:      Thomas Scholz
Author URI:  http://toscho.de
License:     GPL
Plugin URI:  http://wordpress.stackexchange.com/q/24481/
*/
! defined( 'ABSPATH' ) and exit;

add_action( 'admin_menu', 'wpse_24481_demo' );

/**
 * Adds a menu page and a meta box with the same callback function.
 *
 * @return void
 */
function wpse_24481_demo()
{
	$title    = 'Callback Demo';
	$callback = 'wpse_24481_callback';

	add_menu_page( $title, $title, 'edit_posts', 'callback-demo', $callback );
	add_meta_box( 'callback-demo', $title, $callback, 'post' );
}

/**
 * Prints the content.
 *
 * @return void
 */
function wpse_24481_callback()
{
	print 'Here may be dragons.';
}