Tìm Hiểu về Wordpress - part 18 pdf

So instead of displaying something like this in the main posts column: first post title first post content first thumbnail second post title second post content second thumbnail third

Each post now includes its own custom icon that links directly to the single view of

the post itself, as seen in this screenshot of a recent post:

At this point, everything is set up, configured, and working great We are

successfully displaying custom thumbnails that link to their associated posts

Now, to demonstrate the usefulness of WordPress custom fields, let’s remove our

thumbnails from their respective posts and display them as a consecutive gallery

within the sidebar So instead of displaying something like this in the main

posts column:

first post title

first post content

first thumbnail

second post title

second post content

second thumbnail

third post title

third post content

third thumbnail

…and so on…

Instead of using that layout, we’ll display the thumbnails separately in the sidebar:

first thumbnail

second thumbnail third thumbnail

Without using custom fields, it is practically impossible to segregate intra-post data

in this way In other words, if we were to have included the custom-image URL along with the main post content, there would be no practical way of separating the information from the remainder of the post; they would always need to be displayed together

By placing the URL data within a custom field, we are able to display the custom data wherever and however we wish In our current example, we have sequestered the thumbnail images into the sidebar

The catch here is that our get_post_meta() function requires the loop in order

to work Thus, to display our thumbnails in the sidebar, we will need to create a secondary loop within the sidebar itself Fortunately, we have a number of tools at our disposal

For this tutorial, let’s go with everybody’s favorite loop function, query_posts Without going into detail about the query_posts() function, suffice it to say that

it is an excellent way to create multiple, customized loops just about anywhere in your design

Here is the basic structure of our second loop:

<?php query_posts(); ?>

<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

// content goes here

<?php endwhile; endif; ?>

So, after placing that secondary loop into our sidebar, we embellish it as follows:

<?php query_posts('showposts=10&offset=0'); ?>

<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

<a href="<?php the_permalink() ?>" title="<?php the_title(); ?>">

<img src="<?php echo get_post_meta($post->ID, 'thumbnail', true); ?>"

alt="Icon for Post #<?php the_ID(); ?>" />

</a>

<?php endwhile; endif; ?>

As you can see, in the first line, we added two

parameters – the first specifies the total number of

loop cycles (ten, in our example), and the second

indicates that we want the loop to begin with the

most recent item (i.e., no offset) Beyond that bit

of voodoo, we simply copy-&-paste our previously

marked-up get_post_meta() function to replace the

line that says:

// content goes here

Once we upload our newly edited sidebar.php file

to the server, our web pages will feature the desired

result: a nice thumbnail image gallery respectively

linked to the ten most recent posts

Of course, custom fields may be used to associate any

type of information with your posts Custom field

functionality greatly facilitates the use of WordPress

as a CMS Rather than placing all of the information

associated to a post into the “Write” field, Custom

Fields enable you to segregate and subsequently

display different types of content according to any

organizational structure

5.5.4 Users, Roles and Permissions

WordPress provides excellent support for multiple users Any WordPress-powered blog is capable of supporting a wide range of different users, each capable of performing a different set of roles Users are basically anyone who has registered for your site and has a user account What actually defines a user, however, are the different things that they are permitted to do The things that users can do are called “roles,” which by default include the following:

• Administrators - Admins have full access and privileges to everything.

• Editors - Editors may publish and edit posts and manage the posts of others.

• Authors - Authors may publish and edit their own posts, but not the posts

of others

• Contributors - Contributors may write and manage their posts, but not

publish them

• Subscribers - Subscribers are visitors who have registered with your site Their

privileges are no different than those of the common visitor, but subscribers have shown extra interest in your site by providing their information while registering for your site

Each of these roles may be given any number of specific permissions, or

“capabilities.” When applied to a specific role, capabilities enable all users of that particular role to do things like post content, edit posts, moderate comments, and

so on There is no limit as to which capabilities may be enabled for any particular role For example, you could give subscribers more capabilities than administrators The entire user-management system is extremely flexible, enabling you to

customize and configure your WordPress installation for the most complex CMS applications The multiple-user functionality is an essential component of WordPress’ CMS capabilities, and may be enhanced further with a variety of plugins, which we will explore a little later in the chapter

True Subscribers

Even though subscribers don’t

have any real admin privileges,

they are still logged in and thus

the function is_user_logged_

in() will return TRUE

This could be a way to give

registered users extra content.

5.5.5 Categorizing, Tagging, and Custom Taxonomies

WordPress also provides extensive organizational capabilities through the use of a

highly flexible system of categorizing and tagging In a nutshell, categories may be

used to define content that is broadly associated, such as “movies,” “music,” and

“food,” while tags are used to associate finer distinctions, such as “tacos,” “pizza,”

and “cheeseburgers.”

Posts may belong to any number of categories, and then tagged along more

specific characteristics For example, a post categorized under “movies” may be

tagged with “sci-fi,” “space,” “future,” and “aliens.” This level of organization

provides much more power over the structure of your site

In WordPress 2.3, WordPress implemented a new “Taxonomy API” that changed

the way content is categorized and organized Since then, users have been able

to create custom taxonomies to organize their content as effectively as possible

The concept is a little difficult to grasp at first, but if you think of taxonomies as

“groups of tags” then you’ve pretty much got it By default, WordPress organizes

your content with the following three taxonomies:

• category - used for classifying posts into categories

• post_tag - used for tagging posts with various tags

• link_category - used to classify links into categories

As you can see, the tags used for your posts belong to the “post_tag” taxonomy

Likewise, the categories used for your posts belong to the “category” taxonomy,

and link categories belong to the “link_category” taxonomy In general, the tags

and categories that belong to a taxonomy are called “terms.” Thus, your post

tags are all terms of the “post_tag” taxonomy, your categories are all terms of the

“category” taxonomy, and so on

That’s great, but how does all of this new taxonomy mumbo-jumbo help us

use WordPress as a CMS? Basically, taxonomies provide yet another level of

Custom Taxonomies

We cover the “how” of custom taxonomies in Chapter 2.4.7 Update: also check out Chapter 12.2.6 for more information

on the new custom-taxonomy functionality included in WordPress 3.0.

classification and organization for your content Once you create a new taxonomy, you can add as many terms (tags or categories) for it as desired Here is an example

of how this type of organization would be useful:

For a Web-development tutorial site, you could create taxonomies for “topics,”

“languages,” and “applications.” Then, each of these taxonomies would be given

a series of terms that applies to each post So for example, a post on Ajax-powered contact forms could be classified with something like this:

• Topics - ajax, forms, wordpress

• Languages - javascript, php, sql

• Applications - blogs, e-commerce

As you can imagine, this ability to organize your tags into taxonomies opens the doors to new possibilities, and greatly increases your ability to structure your site in elaborate, complex ways

5.5.6 Page Templates

Page Templates enable you to apply custom design and functionality to your different WordPress pages This feature enables you to craft special pages that will process and display content according to your specific needs Consider the following page types and how Page Templates are used with each:

• Search Page - display results in title-only list format and include a

search-term heading

• Archives Page - organize vast amounts of archived content with template tags

and multiple loops

• Tag Archives Page - display a tag cloud along with popular and recently

updated tags Implementing custom Page Templates is easy The default Page template in your

Custom Post Types

Update: for even more

flexibility in creating,

organizing, and displaying

custom-types of content, check

out WordPress’ new Custom

Post-Types functionality

Learn more in Chapters

11.2.10 and 12.2.8.

theme is called “page.php” If no custom page templates have been created, all of

your WordPress Pages will be displayed according to the default page.php template

To create and use a new type of page template – for example, a template with no

sidebar and no title – simply create a file within your theme directory named

“page-nosidebar-notitle.php” and place the following code at the top:

<?php

/*

Template Name: No Sidebar No Title

*/

?>

Then, navigate to the Search Page in the WordPress Admin

and select your custom Page Template as seen in the

screenshot to the right

This new custom Search Page may now include any code

you desire – custom loops, search listings, and so on This

same technique for creating a custom Search Page may

be used to create any number of unique page templates,

thereby facilitating a more flexible system for managing

your online content

5.5.7 Page, Category, and Tag Hierarchies

Another awesome CMS-enabling feature of WordPress involves the ability of users

to create page, category, and even tag hierarchies (via “taxonomies”) whereby any

number and level of “child” items may be created for any given “parent” item

You may create any number of first-level, “child” items, as well as any number of

subsequent-level items

For example, for a page named “Contact” that is used for a sports-related website may feature a parent-child page hierarchy that organizes contact data into logical sections:

Contact [first-level page]

Swim Team [second-level page]

Mary Poppins [third-level page]

Tom Thumb [third-level page]

Jack Horner [third-level page]

Daisy Chain [third-level page]

Soccer Team [second-level page]

Nick Mason [third-level page]

Rick Wright [third-level page]

David Gilmour [third-level page]

Roger Waters [third-level page]

Chess Team [second-level page]

Anakin Skywalker [third-level page]

Han Solo [third-level page]

Obi-Wan Kenobi [third-level page]

Chewbacca [third-level page]

This parent-child functionality provides extremely flexible organizational capabilities to WordPress users, enabling them to manage thousands of pages of content quickly and easily

This same logic is also available to the creation of subordinate categories and tags (see previous section on “Categorizing, tagging, and custom taxonomies” for more information)

5.5.8 Dynamic Menus

Every site needs a solid, well-structured navigational system, and for CMS-type

sites this is especially true Fortunately, WordPress provides a number of powerful

functions that help users create just about every type of menu imaginable Some

examples include:

• <?php wp_list_pages(); ?>

Automatically lists pages in just about every possible configuration imaginable

You can control which pages are shown, limit the appearance of child pages, as

well as format page titles, customize links, specify sort order, and much more

• <?php wp_get_archives(); ?>

Automatically lists yearly, monthly, and even daily archives for your blog

Provides parameters to limit maximum number of items displayed, display

associated post count, and control the formatting of the list itself

• <?php wp_list_categories(); ?>

Displays a list of categories that is completely customizable There are

parameters for everything from excluding specific categories and specifying sort

order to inclusion of feed links control over category depth Powerful stuff!

• <?php wp_tag_cloud(); ?>

Displays a collection of links, known as a “cloud,” for each tag used on your

blog The relative size of each tag may be set based on popularity, or it may

be kept static for a more uniform-looking cloud Several other customizable

features include displaying the tag links in random versus alphabetic order,

inclusion and exclusion of specific tags, and more

As useful as some of this built-in navigational functionality happens to be, there is

always room for improvement Here are a few of the many freely available plugins

that help improve and enhance WordPress’ default navigational system:

• WP-PageNavi http://digwp.com/u/133

Transforms archived page navigation into a row of links to all of your pages,

enabling users (and search engines) to access any archive page with a click

Easy Custom Menus

Update: with version 3.0, WordPress now provides complete control over the creation and display of your menus, all from within the comfort of the WP Admin See Chapter 12.2.7 for details.

• Breadcrumb NavXT http://digwp.com/u/134 Generates locational breadcrumb trails to help visitors where they are in the grand scheme of things The breadcrumb trails are highly customizable

• Pagebar http://digwp.com/u/135

Adds a customizable menu bar to your blog posts, multi-paged posts and paged comments Automatic or manual configurations possible

• Wordpress Navigation List Plugin NAVT http://digwp.com/u/136

Enables complete control over the creation, styling and contents of your site’s navigation Easy drag-n-drop interface makes menu customization a breeze

• WP-dTree http://digwp.com/u/137 Generates navigation trees for your posts, pages, links and categories Uses WordPress’ built-in Scriptaculous library for awesome display effects

• Sub Pages widget http://digwp.com/u/123

Displays the pages which are children from the current root page

For more great navigational plugins, the WordPress Codex is a great place to start: http://digwp.com/u/122

5.6.1 Extending CMS Functionality

As we’ve seen, the built-in CMS functionality is great, but there are many ways to improve upon it by implementing a few choice plugins In this section, we’ll explore some key plugins and explain how they may be used to take WordPress’ CMS

functionality to the next level

5.6.2 CMS-Related Plugins

There are a ton of awesome CMS plugins available for WordPress Here are some of the best:

Breadcrumbs Rock

For large or complex sites,

breadcrumb navigation can

be a hugely beneficial part

of your site’s navigational

system They help users orient

themselves within the site while

enabling quick and easy links

to other parts of the site.