Say you have a bunch of blocks and you want them to be displayed on certain nodes of varying content type based on some criteria like the content type and some CCK fields or taxonomy. You can't do this with the stock block visibility settings without writing custom PHP code.

But we can implement it using some existing basic Drupal building blocks: CCK and Views

1. Create a content type called Visibility Block.

You might have a field for content type where the possible values are returned from code which returns an array of the content types (using function node_get_types()).

2. Then for any fields you want to match, you'll have the same fields in this content type. For example, if one of your content types has a textfield and the possible values are 1, 2, 3, then do the same for Visibility Block.

When you create a Visibility Block, you'll have your block content in the body as normal (optionally you could use Block Reference and create blocks like usual and then link to them in the node instead, but I see no point in the extra effort and redirection), then select the conditions for the pseudo-block being visible.

3. Now create a view called Visibility Blocks Viewed. You'll create block displays, one for each content type that you have a Visibility Block set for which may only be one or two of your c-types.

Create an overridden argument each block display for the content type -field- in Visibility Block. You want to match the content type of the viewed node with the field in the Visibility Block, which are not the same type of thing. So you'll need to convert the argument in code.

You'll call menu_get_object() to get the $node because it's better than "$node = node_load(arg(1));". For the chosen c-type for that block display you will check that the implied node's c-type is what ever type you want to show in this block display because you will also check any fields that are specific to this c-type. Use PHP to supply a value since no argument will be passed in, and have the code load the current node and return the type. Then use PHP for the Validator Options and if the c-type doesn't match then you will display empty text. If you have multiple c-types which share CCK fields then you can put them into a single block display.

4. For each content type, in the chosen block display you will create a new argument for each compared against CCK field. You will pick a field from V-block and then use PHP to return a default value of the currently viewed node's field's value. You won't need to do Validation on these arguments.

5. Finally, you may want to limit the number of nodes returned, maybe just one. Now give this block a title and save it and configure its region in the normal block admin.

--

Why not the normal block visibility settings?

Because there you can't even configure by content type (anymore in D6). You can configure by path glob and by PHP code which overrides the path glob field (including in the database).

So under "Page specific visibility settings", set to "Show if the following PHP code returns TRUE (PHP-mode, experts only).", the field is blocks.pages. Essentially, PHP code works by overriding the pages list.

Why not use Block Page Visibility?

Block Page Visibility (http://drupal.org/project/bpv) enables site developers to centralize the display of blocks to a single PHP function. It is an alternative to controlling display via each block's configure form. The more "sometimes on, sometimes off blocks" that a site uses, the more useful this module becomes.

This takes over the visibility settings of all your blocks by calling:

$sql = 'UPDATE blocks SET visibility = 2, pages = CONCAT("<", "?", "php ", "return bpv_is_visible(\'", module, "-", delta, "\'); ", "?", ">") WHERE status=1 AND theme=\'%s\'';

Sometimes it's easier to configure a block by just whether you're logged in, or whether you're on the front page.

This module doesn't give you any finer grained controls. And you have to configure every block in code. You also lose all your current block visibility settings once you install this module. To use this module you have to implement your own bpv_config or bpv_configuration (I think it's a bug that it's looking for bpv_configuration but actually uses bpv_config).

Before I begin: I'm a Drupal guy. What I say could be construed as being biased. I'll try to be honest though.

When building a website you or your developers have some decisions to make: what language to use, whether to use a framework and which one (depending on language - Zend/CodeIgniter/Symfony/CakePHP for PHP, Ruby on Rails, Django for Python, etc.), whether to use a CMS (WordPress, Joomla, Drupal), whether to self-host or use a blogging service (WordPress.com, Drupal Gardens, Tumblr, Blogger). There is no single right answer.

First, go with the language that is most comfortable. Previously, I had several years experience with both PHP and Python with Python actually being more recent. But few people in Vietnam know Python where many know PHP. But Drupal being in PHP sealed the deal.

Next, is it mostly about managing news-like content? Then go with a blog. Does it need some popular features like user logins and full accounts, social media integration, voting, storing meta-information besides blog text, or otherwise some customization of what kind of content you are storing? Then it's no longer a blog and you should use Drupal. Is it purely ecommerce? Drupal Commerce or Ubercart can do the job, but Magento might be all you need if you are not a developer and as long as you can afford to buy the yearly license fee for it and your website only needs a store of physical items without any other content or custom design.

Do you need something that is more like a web app that's unlike any existing blog, news site, social media site, online store, or corporate website out there? Then maybe you should have a team of developers starting with a web framework (Drupal, as well as being a content management system, is also a content management framework) and start from more basic building blocks.

Some specific use cases:

1) An intranet website for managing some internal corporate data that is really custom to your company. WordPress would not be adequate none of its strong points would apply. Drupal's theming weak points would no longer hurt you here since you just need a professional-looking tool. Best of all Drupal easily gives you and novice users a way to manage your data.

2) Brochure website - like a business card for a store or business with a dozen or so pages of information and some links and a contact form. If you don't already know Drupal then use WordPress. WordPress also has many available commercial themes which can be used. However, a Drupal expert can just as quickly and easily build brochure sites in Drupal.

3) Social network - There are open source packages that are like social-network-in-a-box solutions. But nowadays, social networking is a feature, not a sufficient product alone. In my experience, using these off the shelf packages ends up being too limiting because you will always want to do new things and come up against the limits of the software, even if its open source. This applies to social news software like Pligg, school software like OpenSIS, Open Source Q&A software, forums like vBulletin, etc. Those kinds of sites were once novel and rare but are now just features to be added to larger sites, but they can not reasonable be used to build those larger sites.

WordPress's strong points:

1) Being a blog. It does one thing really well. I have run many WordPress blogs in the past. This blog is built with Drupal though because it's possible to blog with Drupal, and because I've also extended it far beyond blogging with many experiments.

2) Availability of commercial themes. There are a lot of companies making and selling themes for WordPress (this is also a point where Joomla wins over Drupal). There are also plenty of free themes. This is good for people who don't want to put money down on a fully custom design yet and are just happy to use something that looks professional.

3) Usability. Out of the box, WordPress is user friendly and makes it easy to get up and running. Drupal improves at this with every major version but is still something a developer more easily loves than an end user.

Honorable mentions

Mezzanine (http://mezzanine.jupo.org/) is a promising-looking CMS built with Django/Python. If you like Python (like I do) then consider giving it a shot, although it doesn't have nearly the depth and breadth of free modules that Drupal offers nor the size of community.

Cartridge (http://cartridge.jupo.org) is Mezzanine's ecommerce/shopping cart solution. Again, you won't get the community and support like you would with Ubercart but at least you would get to hack in Python!

Mass editing nodes in Drupal can be a chore. If you just want to edit some attribute and set it to a single value for many different nodes then Views Bulk Operations can help. But you may instead want to make some quick changes to the titles, bodies, and CCK fields of a bunch of nodes of a certain type. The default way would be to open each node in a browser tab, go to their edit forms, and then operate on each one individually. Can we come up with a better way?

Multi Node Edit is a module that sounds like it could help. It promises to give you a page with many node edit forms. Unfortunately, this is not the case. By itself, this module is not usable to users. If you write some code to use it like a library you might be able to create a page with many node edit forms on it.

Recommendation: This module isn't useful to most people. It might be useful if you're writing code for a custom page.

Editview (editview) is the easiest to use, you just build Views and select 'Style' of 'Editview' in one of your displays. It works on the whole display, so all fields become editable. Unfortunately, you can't control this. Some fields shouldn't be editable, and so sometimes they just don't appear at all. Other times you may want to view a field but not edit it. Unfortunately, this isn't possible, even when using Global fields. [This issue is tracked here: http://drupal.org/node/635076]

* In my case, I just wanted to get a link to edit the node. I accomplished this by adding a Node: Path field which shows the path/alias editing form.

Recommendation: Use Editview if you're comfortable with building Views. Then you can construct a view of the fields you want to edit, and make it easy to filter the nodes you want to edit.

Editable Fields (editablefields) - 6.2 doesn't integrate with Views, despite the README. 6.3 does integrate but not the way explained in the README.txt. There is no added View type to choose when creating views. The exported content types used for demonstration don't import either. Most fields aren't editable, but if they are there will be a new checkbox for editable with some options. However, the 6.3 version of the module is still quite buggy so it doesn't work at all.

Recommendation: Avoid Editablefields module for now unless you want to just edit fields in the node display.

Drupal sites, like any content sites, naturally receive a lot of spam comments. Any blog or blog-like site which allows unauthenticated or anonymous users to comment on posts or any content is open to spam because spammers just want to have links to their websites displayed by your website for link-building purposes which is important for SEO. Spam comments used to be much more obvious as in blatant ads for penis-enhancing drugs. Nowadays, spammers are using more sophisticated scripts that are still easy to detect - by humans and usually also by spam-detection software. New spam might praise your blog or quote something you said in your blog post or just say something generic, perhaps on a related topic or perhaps not related at all. Then they will have their spam website in the URL field, if not also in the comment text. If the website has keywords which are totally unrelated to your blog, you can bet it's spam.

What can a Drupal website do about spam?

One old solution for spam, a common plugin on WordPress sites, is called Akismet. Akismet is a service and requires you to create an account and get an API key from them. Then they will help you detect spam.

Drupal has something like Akismet but improved and it was created by the Drupal creator himself. It's called Mollom, and it's also a cloud-based service, and you also create an account with them. Mollom is free to use although there are some paid services. I use Mollom on this blog. It catches hundreds of spam comments for me but also lets in a single false negative per day or so. I wouldn't have been able to turn on comments without turning on Mollom as I would immediately be deluged with spam. But I hope that Mollom continues to improve so that I don't even get 1 spam on most days.

Since I still do get some ham and spam comments, I have to process them somehow and report the spams to Mollom so they can improve their algorithms and heuristics for the future. Unfortunately, Drupal's default comments management view doesn't easily let me see if a comment is spam or not. In order to make that decision I need to see the URL and comment text that was saved. If there was no URL, it usually isn't spam, and if there was no URL in the comment text then most certainly it isn't spam. But if there was a link in the text, I need to see what site it links to, and see if the comment is at all intelligent or relevant. You can also tell by looking at any link saved in the URL field. Since Drupal's comment management page doesn't do this, I created a view, which you can import (this is Drupal 6) below.

The thing that Drupal's comment admin page offers is bulk operations. Mollom provides some operations such as report spam to Mollom and delete. This is usually what I want to do. Unfortunately, there's no way to use Mollom's actions in Views with Views Bulk Operations! So until this issue gets resolved (http://drupal.org/node/655846) I've done the next best thing which is to have links to the Mollom management page for each comment. It will still require you to open that page, select the reporting action you want, and then submit the form though. But this workflow has at least saved me some time and now I have removed all the really spammy spam from this site.

$view = new view;
$view->name = 'comments_more';
$view->description = '';
$view->tag = '';
$view->view_php = '';
$view->base_table = 'comments';
$view->is_cacheable = FALSE;
$view->api_version = 2;
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */
$handler = $view->new_display('default', 'Defaults', 'default');
$handler->override_option('fields', array(
  'name' => array(
    'label' => 'Author',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_user' => 1,
    'exclude' => 0,
    'id' => 'name',
    'table' => 'comments',
    'field' => 'name',
    'relationship' => 'none',
  ),
  'homepage' => array(
    'label' => 'Author\'s website',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'display_as_link' => 1,
    'exclude' => 0,
    'id' => 'homepage',
    'table' => 'comments',
    'field' => 'homepage',
    'relationship' => 'none',
  ),
  'comment' => array(
    'label' => 'Body',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'exclude' => 0,
    'id' => 'comment',
    'table' => 'comments',
    'field' => 'comment',
    'relationship' => 'none',
  ),
  'delete_comment' => array(
    'label' => 'Delete link',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'text' => '',
    'exclude' => 0,
    'id' => 'delete_comment',
    'table' => 'comments',
    'field' => 'delete_comment',
    'relationship' => 'none',
  ),
  'edit_comment' => array(
    'label' => 'Edit link',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'text' => '',
    'exclude' => 0,
    'id' => 'edit_comment',
    'table' => 'comments',
    'field' => 'edit_comment',
    'relationship' => 'none',
  ),
  'hostname' => array(
    'label' => 'Hostname',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'exclude' => 0,
    'id' => 'hostname',
    'table' => 'comments',
    'field' => 'hostname',
    'relationship' => 'none',
  ),
  'status' => array(
    'label' => 'In moderation',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'type' => 'yes-no',
    'not' => 0,
    'exclude' => 0,
    'id' => 'status',
    'table' => 'comments',
    'field' => 'status',
    'relationship' => 'none',
  ),
  'timestamp' => array(
    'label' => 'Post date',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'date_format' => 'small',
    'custom_date_format' => '',
    'exclude' => 0,
    'id' => 'timestamp',
    'table' => 'comments',
    'field' => 'timestamp',
    'relationship' => 'none',
  ),
  'view_comment' => array(
    'label' => 'View link',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'text' => '',
    'exclude' => 0,
    'id' => 'view_comment',
    'table' => 'comments',
    'field' => 'view_comment',
    'relationship' => 'none',
  ),
  'cid' => array(
    'label' => 'Mollom',
    'alter' => array(
      'alter_text' => 1,
      'text' => '<a href="/mollom/report/comment/[cid]">Report to Mollom</a>',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'html' => 0,
      'strip_tags' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_comment' => 0,
    'exclude' => 0,
    'id' => 'cid',
    'table' => 'comments',
    'field' => 'cid',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'none',
  ),
));
$handler->override_option('access', array(
  'type' => 'none',
));
$handler->override_option('cache', array(
  'type' => 'none',
));
$handler->override_option('css_class', 'view-comments-more');
$handler->override_option('header', '<style>
.view-comments-more table {
background: white;
position: relative;
z-index: 100;
}
</style>');
$handler->override_option('header_format', '2');
$handler->override_option('header_empty', 0);
$handler->override_option('items_per_page', 30);
$handler->override_option('use_pager', '1');
$handler->override_option('style_plugin', 'table');
$handler->override_option('style_options', array(
  'grouping' => '',
  'override' => 1,
  'sticky' => 0,
  'order' => 'desc',
  'columns' => array(
    'name' => 'name',
    'homepage' => 'homepage',
    'comment' => 'comment',
    'delete_comment' => 'delete_comment',
    'edit_comment' => 'edit_comment',
    'hostname' => 'hostname',
    'status' => 'status',
    'timestamp' => 'timestamp',
    'view_comment' => 'view_comment',
  ),
  'info' => array(
    'name' => array(
      'sortable' => 1,
      'separator' => '',
    ),
    'homepage' => array(
      'sortable' => 1,
      'separator' => '',
    ),
    'comment' => array(
      'separator' => '',
    ),
    'delete_comment' => array(
      'separator' => '',
    ),
    'edit_comment' => array(
      'separator' => '',
    ),
    'hostname' => array(
      'sortable' => 0,
      'separator' => '',
    ),
    'status' => array(
      'sortable' => 0,
      'separator' => '',
    ),
    'timestamp' => array(
      'sortable' => 1,
      'separator' => '',
    ),
    'view_comment' => array(
      'separator' => '',
    ),
  ),
  'default' => 'timestamp',
));
$handler = $view->new_display('page', 'Page', 'page_1');
$handler->override_option('path', 'views/comments_more');
$handler->override_option('menu', array(
  'type' => 'none',
  'title' => '',
  'description' => '',
  'weight' => 0,
  'name' => 'navigation',
));
$handler->override_option('tab_options', array(
  'type' => 'none',
  'title' => '',
  'description' => '',
  'weight' => 0,
  'name' => 'navigation',
));