Showing Blocks while editing a Node in Drupal

No matter how well you think you've designed a form for someone to use, there are always questions. and they are commonly simple ones too. Simple problems deserve simple solutions though, and a help section with a few words is worth the time for any form that you want to get filled in. That being said, a picture is worth a thousand words, and better still, a short video is worth a thousand pictures.
So, the simplest way of adding help to a form is to add content into an <aside/>, kind of like a FAQ section; I like an accordions interface personally. But, within Drupal, adding blocks of information from the context of editing a node of a particular content type is a challenge. Consider the following <?php?> snippet for dealing with this issue.


/*      Show this block only if there is a node of      */
/* content type "Menu Page" that is loaded in edit mode */

$entity_type            = "node";
$valid_content_type     = "menu_page"; /*note the hyphen */
$valid_content_type_alt = "menu-page"; /*  vs. the dash  */
$mode                   = "edit";
$valid_new_node_type = ((arg(1)=="add") AND (arg(2)== $valid_content_type_alt));

/* based on the 0th element of the URL's query string, */
  /*          This is a node so get the NID              */
$nid  = arg(1);
$node = node_load($nid); 
/*    AND vs && both perform a logical 'and' operation,   */
/* but AND stops evaluating as soon as the first argument */
/*                    is evaluated                        */
return ($valid_new_node_type OR ((arg(2)==$mode) AND ($node->type==$valid_content_type)));

Enabling the PHP filter module opens up the opportunity to use php evaluations to display a block and gives you an interface within the block's visibility context section that looks like the diagram below.
A few cautions when using this module. 
  1. Back up your database frequently, and
  2. DO NOT EVER play with this code on a production server.  You will not be popular during business hours of the day! 
Misplacing a comma can send your entire Drupal instance into a tail-spin of Error 500 pages, including the admin pages too! Think about it, do you want anyone asking you, "what happened?", while you're trying to recover from this fatal error.
block visibility settings