I’ve packaged the functionality inside a WordPress plugin called is_child that you can download here. Unzip it, upload it to wp-content/plugins and activate the plugin.

Coding is_child

Doing a quick web search brings up tons of sites providing some sort of is_child or is_tree function. Most of the time it’s something like the following:

function is_child($parent) {
  global $post;
  return $post->post_parent == $parent;
}

This is great and a pretty nice solution. I’ve taken this approach and extended it with the following functionality:

• by default we’ll retrieve all parent pages up to the root node and test whether the current page is part of this tree. This behavior can be disabled though.
• you can supply the name (slug) of a post/page instead of the ID and the function will look it up for you.

All this combined with some error checking makes a great idea even better. Just have a look at the code if you would like to know more about the exact implementation.

Conclusion

We’ve seen that it’s very easy to test whether the current page is a child of another page or part of a certain tree in your page hierarchy. Packaging this into a plugin or placing the necessary code into your theme’s functions.php allows you to display certain content on particular pages only. In case you’re using the Widget logic plugin you now can display widgets on pages belonging to a particular subtree of your pages only, which is great.

You can download the plugin here, unzip it, upload it to your wp-content/plugins directory and activate it.

How to

Using this plugin is super simple: just add a custom field named cnote to a post/page and enter the content that should appear next to the comment form into its value field.

Here’s an example:

When WordPress renders the page, the plugin will pick up the content of your custom field and display its content next to your comment form. It may look like so:

The plugin expects that you enter some text, so it inserts your content into a p element. This element has got a class cnote helping you to style the notes with CSS.

The code

In case you’re developer and want to know more about the code just have a look at the plugin, it’s really straight forward. What it does is this: look out for a custom field named cnote, if it’s present we’ll output it’s contents otherwise nothing happens.

$note = get_post_meta($post_id, 'cnote', true);
if (empty($note)) return;
echo '<p>', $note, '</p>';

This gets registered with the comment_form action and will be executed once the theme calls this action.

Conclusion

Using custom fields we can add hints to comment forms on a post/page basis. This technique may be really helpful in case you would like to tell the user something special just before he fills out the comment form.

Generating the quiz

We’re going to generate very easy mathematical equations to prevent spam bots from filling out the form. To make things really easy we ask the user to add two numbers where the sum is always smaller than ten. This way it’s a matter of a second to fill out the quiz and the user can complete the form really fast.

Here’s a small shell script that generates the necessary code for the quiz tag.

for i in `seq 1 9`; do
  for j in `seq 1 9`; do
    sum=`expr $i + $j`
    test $sum -gt 9 && continue
    echo -n "\"$i+$j=?|$sum\" "
  done
done
echo

The same script in Perl can be easily executed with perl -e.

for ($i = 1; $i <= 9; $i++) {
  for ($j = 1; $j <= 9; $j++) {
    $sum=$i+$j;
    next unless $sum <= 9;
    print "\"$i+$j=?|$sum\" ";
  }
}
print "\n"'

Use whatever works for you.

Going one step further

Maybe you want to adjust the code above to suit your needs but you’re way too lazy to do this. I thought about that too and setup the following JavaScript. Change the values as you see fit and copy the corresponding code to your form; maybe you want to set the name – quiz-4711 – to something else.

Conclusion

Using a quiz along with Contact Form 7 helped me to eliminate spam submitted through the forms I’ve set up. The quiz is super easy and shouldn’t annoy the user. Since I’ve used the scripts above numerous times I thought about sharing them with everybody who’d like to use the quiz this way.

I’ve found the generator meta tag in my fresh installation of WordPress 2.7 here, there and everywhere:

/* In the HTML header */
<meta name="generator" content="WordPress 2.7" />
 
/* In the RSS feed */
<generator>http://wordpress.org/?v=2.7</generator>
 
/* In the Atom feed */
<generator uri="http://wordpress.org/"
 version="2.7">WordPress</generator>

And the code suggests that there’re even more places where this tag might show up.

How to remove it completely

If you’re doing some security through obscurity you might have googled a little bit and found the solutions that use the following piece of PHP code just unsatisfactory:

remove_action('wp_head', 'wp_generator');

So let’s remove it completely like so:

function rm_generator_filter() { return ''; }
add_filter('the_generator', 'rm_generator_filter');

This will remove the tag everywhere: from the HTML, the RSS and the Atom feed, et cetera.

WordPress’ world of possibilities…

Now I’d like to present another solution that might make sense: What about removing the generator tag almost everywhere but not in case of RDF content? Since RDF is widely used as a format for data mining applications why not show the information to these web robots? You could do this like so:

function rm_generator_filter() { return ''; }
 
if (function_exists('add_filter')) {
  $types = array('html', 'xhtml', 'atom', 'rss2',
                 /*'rdf',*/ 'comment', 'export');
  foreach ($types as $type)
    add_filter('get_the_generator_'.$type, 'rm_generator_filter');
}

What it does is adding a filter for every type but RDF returning just and empty string for the generator meta tag.

Although this doesn’t make much sense from the standpoint of security through obscurity because making the information available in just one place would compromise your security anyway, I just wanted to show that WordPress is flexible enough to do something like this.

Download

You can download the above code packaged in a plugin here. Have a look at the code and checkout the define in line 30: set it to true or false whether you’d like to remove the tag completely or not; the default is to remove it just everywhere.

Then I was told that the plugin as I built it wasn’t working with Internet Explorer. I booted up Windows and came up with a solution to this problem that I want to share here: don’t embed SmoothGallery and Prototype on the same page.

SmoothGallery and Prototype

Jonathan warns us on the download page that he doesn’t recommend the namespaced version of SmoothGallery because of incompatible frameworks like Prototype or jQuery.

I did some tests and found out that SmoothGallery doesn’t work with Prototype at all – if you’re using Internet Explorer. You can download the tests here: Just open the HTML files and check whether the gallery is present.

Have a look at my results:

If you try to use SmoothGallery with Prototype enabled in Internet Explorer the gallery won’t be rendered; I have tested this with version 6 and 7 of IE. No problems with Firefox or Safari though.

There’s another thing I noticed: if you change the order of the script entries in the HTML header IE will display the images of the gallery in two different ways. Either you’ll be able to see all pictures in the gallery or you’ll just see the first one.

Another observation is that SmoothGallery breaks apart if you insert an a tag with the name set to options. Once you’ve inserted such an anchor IE won’t render the gallery; again no problems with Firefox or Safari.

Conclusion

I’ve just explained what I observed testing JonDesign’s SmoothGallery and Prototype with Internet Explorer, Firefox and Safari. I didn’t take a look at the JavaScript and didn’t search for a solution there.

If you want IE users to watch a smooth gallery on your website it seems that there’s no other way than to get rid of Prototype – remove it at least from the specific page you’re using a SmoothGallery on.

The translation will be integrated in the next release of the plugin which you may download here.

Screenshots

If you’re interested have a look at the nice look of the German translation.