gistfile1.php

<?php
/*
Plugin Name: Post Page Binder
Plugin URI: http://risermedia.com
Description: A way to bind posts and pages using custom meta data.
Version: 1
Author: Merrick Christensen
Author URI: http://risermedia.com
*/

defined('ABSPATH') or die('No direct script access.');

class Post_Page_Binder
{
	public function __construct()
	{
		add_action('admin_menu', array($this, 'action_add_pages_box'));
		add_action('save_post', array($this, 'action_save_post'));
	}
	
	public function action_add_pages_box()
	{
		add_meta_box('Did You Know?', __( 'Did You Know?', 'did you know?' ), array($this, 'pages_box'), 'page', 'side', 'low');
	}
	
	public function pages_box()
	{
		global $post;
		global $wpdb;

		$page_ids = $wpdb->get_results('SELECT ID FROM wp_posts WHERE post_type = "did_you_know" AND post_status = "publish" GROUP BY ID');
		
		
		$html = NULL;
		$html .= '<p><strong>Did You Know?</strong></p>';
		$html .= '<select name="did_you_know_id">';
		$html .= '<option value="NULL">Select One</option>';
		foreach($page_ids as $page_id)
		{
			$html .= '<option value="'.$page_id->ID.'">'.get_the_title($page_id->ID).'</option>';
		}
		$html .= '</select>';
		$html .= '<p>If this uses a "Custom Product" category page template, what "Did You Know?" content would you like featured?</p>';
		
		echo $html;
	}
	
	public function action_save_post($post_id)
	{
print_r($_POST); // works and contains did_you_know_id key

		echo('>>>>>'.$_POST['did_you_know_id']); // Fails... what!?
		if( ! empty($_POST['did_you_know_id']))
		{
			echo $_POST['did_you_know_id'];
			/*if( ! update_post_meta($post_id, 'did_you_know_id', $_POST['page']))
			{
				add_post_meta($post_id, 'did_you_know_id', $_POST['page'], true);
			}*/
		}
	}
}

new Post_Page_Binder();