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WordPress 3: Building Child Themes

Adding Related Posts feature to posts


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WordPress 3: Building Child Themes

with Morten Rand-Hendriksen

Video: Adding Related Posts feature to posts

A simple way of extending the functionality of a WordPress site is by adding plugins. And most plugins work pretty much out of the box. But there are many great plugins out there that either require you to make changes to your theme or that allow you to use them in more advanced ways by including their functions into your theme. This is a great use for child themes and done right, it can be both simple and effective. To give you an example of how this works, let's add a list of related posts at the bottom of our single post view using the Yet Another Related Posts Plugin and a custom function.
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  1. 6m 59s
    1. Welcome
      1m 6s
    2. Using the exercise files
      1m 34s
    3. What you need to know before watching this course
      1m 29s
    4. Getting the right tools for theme creation
      2m 50s
  2. 17m 2s
    1. What is a WordPress child theme and when should you use it?
      2m 38s
    2. Picking a parent theme
      3m 55s
    3. Making sure you have the Twenty Twelve parent theme
      1m 50s
    4. Creating and activating a basic child theme
      4m 20s
    5. Importing parent theme styles
      4m 19s
  3. 16m 2s
    1. Using the developer tools
      3m 53s
    2. Modifying existing styles
      4m 24s
    3. Adding space between paragraphs
      4m 7s
    4. Changing font family styles
      3m 38s
  4. 31m 47s
    1. Understanding the WordPress template hierarchy
      3m 12s
    2. Modifying existing templates
      2m 33s
    3. Moving the header image
      4m 29s
    4. Adding Related Posts feature to posts
      6m 26s
    5. Creating custom page templates
      5m 43s
    6. Using conditional statements for customized effects
      5m 41s
    7. Creating custom header, footer, and sidebar templates
      3m 43s
  5. 17m 5s
    1. Understanding the different index pages and what they do
      4m 6s
    2. Adding author, date, and time information to the index loop
      7m 15s
    3. Changing the appearance of category index pages
      5m 44s
  6. 43m 5s
    1. Introducing functions.php
      3m 24s
    2. Overriding existing functions
      3m 23s
    3. Adding pagination to index pages
      5m 49s
    4. Adding to existing functions
      3m 21s
    5. Adding a new footer menu to Twenty Twelve
      6m 24s
    6. Adding a new widgetized area to pages
      4m 9s
    7. Adding static content to the sidebar
      7m 44s
    8. Replacing existing functions
      2m 36s
    9. Adding a Google font through a function
      6m 15s
  7. 10m 24s
    1. Adding new featured image sizes
      5m 41s
    2. Adding featured images to posts and pages
      4m 43s
  8. 31m 1s
    1. Adding a welcome message to the front page
      1m 22s
    2. Displaying page content in an index page
      7m 42s
    3. Hooking in a featured image
      4m 34s
    4. Making the welcome message responsive
      6m 27s
    5. Restricting content to the first page of the blog
      4m 22s
    6. Adding a jQuery function to show or hide the welcome message
      6m 34s
  9. 10m 23s
    1. Adding a custom favicon
      3m 58s
    2. Adding a custom screenshot
      2m 29s
    3. Adding footer information
      3m 56s
  10. 7m 14s
    1. What to do when a child theme crashes your website
      4m 38s
    2. Updating parent and child themes
      2m 36s

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WordPress 3: Building Child Themes
3h 11m Intermediate Jun 23, 2011 Updated Nov 27, 2012

Viewers: in countries Watching now:

Create a child theme based on an existing parent theme in WordPress and change the functionality, presentation, or styling of your website. In this course, author Morten Rand-Hendriksen shows how to use the default WordPress theme, Twenty Twelve, as a basis for a new child theme and add custom menus; new headers, sidebars, and footers; and index pages with widgets and pagination to your site. The course also demonstrates how to add a responsive welcome message to your front page using PHP and jQuery, and how to edit the many templates found in a WordPress theme. Morten explains how to perform these changes using any code editor, the developer tools in the Chrome browser, and WordPress.

Topics include:
  • Picking a parent theme
  • Creating and activating a basic WordPress child theme
  • Using the developer tools
  • Changing the header image size
  • Using conditional statements for customized effects
  • Adding custom menus to the child theme and/or a template
  • Changing the default footer content
  • Adding featured images to posts
  • Changing the display of meta content (such as date, author, category, etc.)
  • Excluding categories from the front page with custom queries
  • Including functions from external files
  • Identifying and fixing common mistakes
Subjects:
Web CMS
Software:
WordPress
Author:
Morten Rand-Hendriksen

Adding Related Posts feature to posts

A simple way of extending the functionality of a WordPress site is by adding plugins. And most plugins work pretty much out of the box. But there are many great plugins out there that either require you to make changes to your theme or that allow you to use them in more advanced ways by including their functions into your theme. This is a great use for child themes and done right, it can be both simple and effective. To give you an example of how this works, let's add a list of related posts at the bottom of our single post view using the Yet Another Related Posts Plugin and a custom function.

The Yet Another Related Posts Plugin, or YARPP as it's called, is a great plug-in that adds a list of related posts wherever you want it in your site. The great thing about the plugin is it actually reads your content and figures out what posts relate to what other posts. So that when people read a post on your site at the bottom or at the top of the site, they find lists of other related posts they're probably going to be interested in. That keeps them on your site longer and it also makes for a better experience for the people that visit your site.

First we need to add the plugin to our sites. So I'll go to the Dashboard, go to Plugins > Add New, and here I'll simply search for YARPP. I find it down here, Yet Another Related Posts Plugin, I'll install it, activate it, and then I get a flag that says I've installed it and then I need to go configure it. So I'll directly to the Related Posts settings page. Now if you're using BitNami like I am, you may get this warning message at the very top here that says that things aren't working the way they're supposed to in the database.

This is an issue that's related to how BitNami sets up a database. And you're very unlikely to see this on a website that lives on a web server on the web. So just ignore it and move on. When you install YARPP, you're most likely going to see that Automatically Display Related Posts is activated by default. If it is, and you go to a single post, scroll down to the bottom, you'll find that it either says no related posts or that there is a list of related posts at the bottom of your posts.

This is one that's auto inserted, and it's always inserted before this content at the bottom of each post. But what if you want to place it somewhere else? Let's say, I want to have this list appear beneath the meta content and in place of the standard navigation that points you to the previous and next post, because I think that navigation is silly. In that case, I need to turn off the automatic insert and insert the function manually instead. And I can do that, because YARPP allows me to do it. So I'll go back to the settings for YARPP.

Turn off Automatically Display Related Posts and then hover my mouse over this more tag and it tells me that I can use a function called related_posts to display the related posts in my template file. To get that to work, I first have to go to Twenty Twelve, find the template I want to edit, in this case single.php, copy it into my child theme, open the child theme, single.php file in my code editor, and then find the content I want to replace, which is right here, nav-single, and also add in the content I want to replace it with.

First, I'm going to remove this content I don't want. This is the navigation that points on the previous and next post and I think that's kind of silly. So I'm going to take it out and in its place I'm going to place that function that came with YARPP. So I'll put in PHP delimiters and then I'll put in the function. I'll save the template and reload my single post. And now you see that in place of the navigation that was here previously, we now see no related posts.

I also see that I forgot to deactivate the automatic insert. So I'll go back to related posts, make sure it's unchecked, click Save Changes, reload my single posts and now you see no related posts appears here. But there is a caveat here. The function Related Posts is associated with the plugin, so what happens if I deactivate the plugin? I'll go into Plugins > Installed Plugins and deactivate Yet Another Related Posts.

And now when I reload the single post here, you'll see something very strange happen. The post will generate, but then it terminate at the bottom here, before it's finished. That's because in my template file, I'm calling a function that no longer exists. So here's the rule of thumb, if you ever add a function from a plugin, you must wrap it in a conditional statement that tests to see if that function exists. The function you're going to wrap in is not surprisingly called function_exists.

So we'll simply ask, if function_exists, give the name of the function, and then we say, as long as the function exists due the following. In this case, run the function and then end the conditional statement, save the template file and reload the page, and now the page works even though the function did not kick in.

And if I go back to WordPress, reactivate Yet Another Related Posts Plugin and reload the page again, the function reappears. If you use plugins in your site, I guarantee you'll come across ones that require you to add functions or other elements to your template files. Using a child theme and wrapping these plugin functions and conditional function_exists tags ensures that you get the full use out of your plugin, that if the plugin breaks or gets deactivated, or uninstalled, it doesn't break your site.

And that if something disastrous happens when you install the new function, all you have to do is remove the template file from your child name and everything goes back to normal again.

Find answers to the most frequently asked questions about WordPress 3: Building Child Themes.


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Q: The 2010 version of this course no longer covers installing BitNami. Can you provide directions?
A: Instructions on how to install WordPress using BitNami can be found at
 http://bitnami.org/stack/wordpress. Use the "Installer" option. 
It is pretty straight forward and almost impossible to mess up.

lynda.com also has a dedicated course on WAMP and MAMP (Installing Apache, MySQL, and PHP) that is relevant and you might find helpful.
Q:When looking to download PHP development tool at www.eclipse.org/pdt/, as advised by Morten, but when accessing the site via this link, the screenshot in the movie is very different from what it takes you to on the website.
A: Eclipse has a very active developer cycle and updates quite frequently. The interface changes all the time. I recommend using Notepad++ (Windows) or TextWrangler (Mac) instead. They perform the same function but are far less cumbersome to deal with.
Q: This course was updated on 11/27/2012. What changed?
A: This course was heavily revised to reflect changes to the default WordPress parent theme, Twenty Twelve, and updates to WordPress's functionality. The entire course was re-recorded to reflect changes to the interface. Then we added new movies on text styling, the Related Posts feature, and the welcome message features. There are also two brand new chapters, "Modifying and Adding Functions" and "Working with Featured Images." We recommend that members who have seen the whole course start again from the beginning to get the most benefit from this update.
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