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And that’s all there is to it! Depending on placement of the function call, your
comments area should now feature quick and easy “spam” and “delete” buttons
next to each individual comment. Even better, this improved function is version-
independent, backwards-compatible, and thus will work for any version of
WordPress.
5.3.5 Example #2: Sitewide Shortcode Functionality
In short, WordPress shortcodes are shortcuts for frequently used content such as
links, images, and titles. As you blog, instead of writing out the entire link to your
homepage, for example, shortcodes enable you to simply write “[home]” anywhere
you would like the link to appear.
Of course, more complex shortcodes are possible, including shortcodes that include
varying attributes. This functionality is made possible thanks to a set of functions
called the Shortcode API that was introduced in WordPress 2.5. When a shortcode
is encountered, it is processed by the WordPress API and its associated functionality
is executed.
The easiest way to implement shortcode functionality is to specify your shortcodes
via the functions.php file. Here is a PHP function that will convert the [home]
shortcode into a link to your site’s homepage:
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When you are building a theme, and the circumstance comes up
where you need to create a link to a specific page hard-baked
right into the theme, there is a function you should be using.
Not great
<a href="/contact/">Contact</a>
Much better
<a href="<?php echo get_permalink(12); ?>">Contact</a>
That “12” would be the ID of the Post or Page. Why is
this better?
• If the slug ever changes, you are still cool.
• If the site moves from a sub directory (like if you were

you needed to add a special class name to the link or something
(but only occasionally).
Providing text
[permalink id=49 text='providing text']
This way returns a fully formatted anchor link back, using the
text you pass.
Easy Shortcode Permalinks
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<?php // shortcode for homepage link
function myHomePage() {
return '<a href="http://domain.tld/"
title="My Website Homepage">My Homepage</a>';
}
add_shortcode('home', 'myHomePage');
?>
Place this function in your theme’s functions.php file, and then call the function
by using the shortcode. Simply write “[home]” anywhere in your blog post and
WordPress will run the myHomePage function and display the link to your
homepage.
5.3.6 Example #3: Transferring Plugins to functions.php
As we have seen in the previous two examples, the functions.php file is perfect for
extending the functionality of WordPress. In addition to these types of functions,
we can also move entire plugins into the functions.php file.
One reason for doing this involves isolating the plugin’s functionality to a specific
theme. Plugin functionality affects all themes, whereas a functions.php file will
only affect its associated theme.
Transferring the contents of most plugins is as simple as copying and pasting
the contents into the functions.php file. Some plugins may require additional
modifications to work properly when relocated to the functions.php.
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WordPress Functionality
So far we have explored the two most common ways of extending WordPress
functionality, namely, plugins and the functions.php file. In addition to these
methods, you may also implement custom functionality directly within your theme
template files.
5.4.2 Functions Within Theme Files
As discussed in the Themes Chapter of this book, theme template files contain
numerous template tags, PHP scripts, and (X)HTML markup. Within these files,
designers and developers may place just about any custom functionality they wish.
For example, the previous functions.php example for “Easy Admin Buttons” could
be placed directly within the theme file instead. Within the comment loop, we
could add the script as follows:
<p><?php comment_author_link(); ?><p>
<p><?php if (current_user_can('edit_post')) {
echo '<a href="'.get_bloginfo('wpurl').'/wp-admin/comment.php
?action=cdc&c='.comment_ID().'">Delete</a>';
echo ' | <a href="'.get_bloginfo('wpurl').'/wp-admin/comment.php
?action=cdc&dt=spam&c='.comment_ID().'">Spam</a>';
} ?></p>
<?php comment_text(); ?>
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This setup will output the following markup, which will vary depending on the
actual content of your site:
<p><a href='http://domain.tld/' rel='external nofollow'>Author</a></p>
<p><a href="http://domain.tld/wp-admin/comment.php
?action=cdc&c=123">Delete</a> | <a href="http://domain.tld/wp-admin/
comment.php?action=cdc&dt=spam&c=123">Spam</a></p>
<p>Hello, thanks for this article, it is exactly what I needed!</p>
The key to placing functions directly in your theme template files involves
removing the function declaration from the function itself.

to hack a few lines of core code to do the job. So, rather than pretend that people
don’t do it, here are some tips for when you find yourself doing the “evil” deed:
Super-Easy Post-Thumbnails
Surfing the Web, you will notice that many blogs include a thumbnail image for each post. For example, at
DigWP.com, we attach a thumbnail to every post to help improve the user-experience for visitors. Before
WordPress version 2.9, including these post-thumbnails required use of custom-fields, but now with 2.9
and better, WordPress features a much easier way of doing it. To get started with post thumbnails, add the
following line of code to your theme’s functions.php file:
if (function_exists('add_theme_support')) { add_theme_support('post-thumbnails'); }
With that code in place, go to write or edit a post as usual in the Admin, and click on the “Set Thumbnail”
link in the “Post Thumbnail” panel. From there, select and tag your image from within the Media Library.
Then, to display your post thumbnails in your theme, add the following template tag within the loop:
<?php has_post_thumbnail(); ?>
There is much more that can be done with WordPress' post-thumbnail feature. To learn
more about additional tags and ways to customize things, check out Chapter 11.2.7.
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• Don’t hack the core unless you have absolutely no other option
• Do your research and understand exactly what you are doing
• Create a “read-me-before-updating” text le that details the changes
Bottom line: Before hacking the core, do your research, know what you are
doing, and make absolutely certain that no other options exist. Also, take good
notes and refer to them before every future WordPress upgrade. You never know,
you may actually learn something new from digging around under the hood!
5.5.1 WordPress as a Content
Management System (CMS)
As we have seen, the possibilities for extending WordPress functionality are
virtually endless. What began as a humble blogging platform called b2/cafelog way
back in 2001 is now robust and flexible enough to serve as a highly customizable
Content Management System (CMS).
One of the main distinctions between a CMS and a simple blog involves the

thumbnail-01.jpg”, we have associated the thumbnail
with our post in such a way that will enable us to display it
anywhere on the page.
With the custom fields added to our posts, we are now ready to tap into some core
WordPress functionality and display our custom post-images in the desired fashion.
The function we will be using to retrieve the custom images is get_post_meta(),
which is a native WordPress function designed to retrieve specific custom-field key
values. The get_post_meta() function takes the following three parameters:
$post_id - defines the post from which the custom-field
data is called
$key - defines the key of the desired custom-field meta
value
$single - specifies whether to return the data as a string or
as an array
Good
Using custom elds for post
thumbnails is the way to go.
Bad
Putting post thumbnails in the
content itself isn’t very exible.
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Plugged into the get_post_meta() function, these parameters look like this:
<?php get_post_meta($post_id, '$key', $single); ?>
To specify the ID parameter, $post_id, for each post, we use “$post->ID”, which
requires the function to be placed within the loop. For the $key parameter, we
will use the name of the target key, which in this case is “thumbnail”. And finally,
because we want the key value returned as a string, we use “true” for the $single
parameter. At this point our get_post_meta() function looks like this:
<?php get_post_meta($post->ID, 'thumbnail', true); ?>
And we are almost there. As is, this code will simply return the custom-field value