art-exhibition

What Developers Need to Know About Theme Design

Making a theme is really exciting. It’s a great way to practice your coding skills. It could be a good way to bring in some extra pocket change. Best yet, seeing someone use something you’ve built is incredibly rewarding.

I’ve watched the quality of theme design get better and better in the WordPress.org directory in the last few years, but I still see a lot of themes that look the same. Free themes still lag behind premium themes in terms of design quality. You can help change all that. You don’t need a design background to make good design decisions: a developer conscious of design can still make a good-looking theme.

Here are a few general tips and tricks you can apply to your themes to give them a solid design base, regardless of your background.

Pick a Direction

When planning out your new theme, have a specific user or use case in mind. That use case shouldn’t be “a theme for everyone.” Your use case can still be pretty broad — “a modern theme for small businesses” is still targeted enough for your ideal user to solve a specific goal by using your theme. Alternately, you can get super specific, giving yourself a prompt like “a food blogging theme targeting smartphone photographers.” Each theme idea has a different set of constraints, and by embracing and sticking to these constraints, you can make better themes.

Once you have a direction in mind, think through that scenario and what your target users would need. The more you imagine how people are going to use your theme, the stronger your concept becomes.

For a modern business theme, think about what a great business website needs. If the company has a physical location, site visitors need an easy way to find an address or directions. People visiting the site need a way to contact the business, via phone, email, or contact form. The theme needs strong page templates, but probably not a unique blog template. It probably needs a navigation bar that can support up to a dozen or more pages at various levels. Typography should probably be strong and serious. A business might also need to display their products, so you could consider adding support for popular e-commerce plugins.

On the other hand, an amateur food blogger, especially if they don’t have a nice camera, needs a theme that focuses more on super strong typography. Photos should be present, but de-emphasized in case they aren’t top-quality. The theme’s users need a way to easily display recipes. Maybe this means building a plugin that pairs with the theme for extra feature support, or maybe it means really nice post styling. A variety of page templates probably aren’t extremely important, but well-styled category archive templates are. Type can have a little more personality, but still has to be readable.

In both situations, you want to have a strong responsive design so site visitors can browse on their phones or tablets. After all, 50% of web traffic comes from mobile devices.

Look at other themes and websites that fit within your use case. Find five really great ones and figure out what makes them great. Take these insights and apply them to your theme.

Visual Design

Typography

Typography is probably the most important part of the vast majority of themes. What’s a site without text? Type needs to be clear, readable, and context-appropriate. There’s a couple rules of thumb you can use to make sure your theme’s typography looks good.

The hardest part of theme typography is picking the right fonts. The “popular” sorting option on Google Fonts is a surprisingly okay place to start looking for a font to use. Try to pick fonts that have multiple weights. Depending on the font, a light or semibold weight might be more appropriate than just regular or bold. At the very least, avoid using fonts that don’t come with bold or italic. There is (finally)! a “number of styles” filter in Google Fonts that you can also browse through. Don’t trust Google’s recommended font pairings — they’re actually pretty poor.

If you want to combine a serif and a sans-serif and you’re unsure which typefaces to pick, go for a font family. These are built to have similar features and will naturally pair well. Some families on Google Fonts include Merriweather Sans and Serif, PT Sans and Serif, and Noto Sans and Serif.

When in doubt, use font combinations from sites you like.

Once you’ve chosen your font(s), you need to style your text to be readable. This means using appropriate font sizing. Don’t make someone squint! Use at least 14px or higher for your body text. If 14px looks too small, don’t be afraid to go up to 16px, or even 18px.

One of the biggest issues I see concerning type on themes is an overall lack of line height, which is the space between each line of text. As a general rule of thumb, my headers are always between 1.2-1.4* the size of my font, and my body text is almost always between 1.4-1.6* the size of your font. And the awesome thing about line-height is you can even just use line-height: 1.4 instead of having to calculate the actual pixel value.

As a general rule, paragraphs shouldn’t be more than 50- 75 characters long. This helps keep them nice and readable.

Finally, limit the number of font styles. I mentioned earlier that you should look for fonts that have multiple font weights. While you should seek these out, don’t combine too many different font weights and sizes, since they negatively impact your content’s hierarchy and flow.

Color

There is a lot of psychology around color. You don’t need to be an expert in color, but learn a little bit before you pick them for your theme. Colors also have different meanings in different cultures, so keep your audience in mind when picking your palette. For a good introduction to color theory, watch Aaron Jorbin’s presentation on WordPress.tv.

Color also affects whether or not your users will be able to view your theme. Keep in mind contrast when designing your themes — contrast that’s too high or too low makes it hard for people, especially people with visual impairments, to read your text and navigate through the site. Keep in mind people with low vision or color blindness.

Don’t use too many bright or bold colors. They’re great for emphasis and drawing attention to specific parts of the page, but too many strong colors can make your theme hard to look at, or can make it difficult for people to find the most important content on the page.

Soften your blacks. Pure black doesn’t really exist in the world around us, and pure black on the web ends up looking harsh and unnatural. Add hints of color to your black by going up and right in most color pickers, or go for a dark grey.

If you’re struggling with color, here’s some things you can do:

  • Stick to dark text on a light background with one or two accent colors. You can’t go wrong with dark grey text on white.
  • Use a site like Adobe Color or Colour Lovers to find nice palettes.
  • Borrow color palettes from sites you like.

Whitespace

Let everything breathe. Use ample white space between separate elements in your theme.

Finding the right balance of whitespace is hard. When in doubt, l o o s e n  t h i n g s  u p  a  l i t t l e. (Just not your lowercase text — only add letter spacing to uppercase text.)

Details

Don’t go crazy with the details. Less is more.

For example, consider if the drop-shadow you’re using adds a necessary sense of depth to your theme, or if it’s purely decorative. If it’s necessary, tone it down a little. In general, don’t use drop-shadows darker than 25% opacity. The same can be said for gradients; try to keep gradients subtle.

Use animation sparingly. I mean really sparingly. Inappropriate animation is jarring and detracts from your theme. Motion should only be used to show change, not for decoration.

UX Design

There is nothing worse than finding a theme that looks awesome and does what you need, only to install and activate it and find a thousand options you need to hand-configure to make it look like the demo.

Many of WordPress’s core philosophies revolve around simplicity and ease of use:

  • Great software should work with little configuration and setup.
  • Design for the majority.
  • Decisions, not options.
  • Clean, lean, and mean.
  • Striving for simplicity.

You should take these core philosophies to heart when creating your themes. Cut the number of options down to what’s absolutely necessary. For example, instead of letting people control every single color in your theme, let them choose two or three and generate a color scheme based on those colors. Make smart defaults and informed assumptions. If you include options that can be previewed, put them in the Customizer. Stop using gigantic theme options and settings pages. They are almost universally a bad experience for users.

Lastly — user test! If you’re creating a premium theme, you owe it to your users to make your theme as easy to set up and use as possible. UserTesting.com is relatively cheap and easy. Running as few as 3 user tests will catch the majority of your theme’s issues.

Free theme? No budget? Ask around for some beta testers. Don’t want to? Then at the very least, set up your theme on a couple different demo sites. Try it on one totally new, empty site, and then try setting it up on a site that already has content. Record your screen as you set it up. If you did well and remembered where everything was — awesome! You can now use that video as documentation. Did you struggle? Figure out where the process broke down, and fix it.

Love the idea of user testing? Read Rocket Surgery Made Easy by Steve Krug. It’s short, concise, and explains everything you need to know to run a good user test.

You don’t need to be a designer to make a good theme — you just need to be conscious of your design decisions. Now go forth and theme!

Hand turning up volume on sound board

Up Your Theming Game by Reviewing Themes

You have strong theme sense, you’ve started working on or released a theme into the world, and you want to get better. You can do just that and do it without one design iteration or a single line of code.

Join the WordPress Theme Review team.

Few communities like the WordPress community exist in the world. You’ll find many opportunities to make behind-the-scenes contributions that have huge ripple effects. The WordPress Theme Review team is one of those opportunities. If you’re a themer at any level, you can learn more than you ever would creating themes by yourself.

You’ll get to know the theme requirements. Reviewing themes taps you into the pulse of WordPress theming and its best practices. You’ll become an expert with the theme requirements in no time. With that knowledge, you’ll be able to create better themes, and create them faster. Plus, you don’t really know something until you have to explain it with clarity to someone else. You’ll do that with each review.

You can contribute without code. You know and I know it, seeing your name on the WordPress credits page is a thrill. However, you can help WordPress in many ways without knowing the ins and outs of code. Contributing to the Theme Review team can improve your code skills fast. You’ll read more code and provide more feedback than you could on your own. Each time a theme you reviewed goes live, you’ll feel just as good as seeing your name on the WordPress credits page – promise.

See better themes everywhere. This should go without saying, but with each theme you review, you’ll have a chance to make it a little better. That means better themes for the users of WordPress and better experiences across millions of sites. More people will be able to find a theme that fits them perfectly, and be more willing to publish and share their ideas with the world. What a great way to spend a few hours of your time.

You’ll find inspiration and become a better themer. Each new theme review will expose you to new ideas, from design to code to tools to process and so much more. Every theme has its own dose of inspiration. Take it in. Experiment. Iterate. Repeat.

Help people create. At the end of the day, you’re doing something incredibly special – you’re helping someone’s creation come to life. I love theming because you get to build something from scratch. You mix some art, science, and part of you into something that has never existed before. Creating is good, helping others create is even better.

Learn from shared knowledge and teamwork. When reviewing a theme, you’re not just helping or teaching – you’re on the same team. You have so much to share with each other. You both have the same goal. It’s not about who knows more, it’s about how much you know together. See what you can do with it.

Learn about the WordPress Theme Review team and become a reviewer today.

Happy theming theme reviewing!

What’s new in WordPress 4.1 for Theme Developers?

WordPress 4.1 has been a long-awaited release for theme developers. Not only does this version ship with the awesome Twenty Fifteen theme, but also with a number of new functions and features that make theme development faster and easier. In this post, we’ll have a look at these new features and show you how to use them in your themes.

Auto-generated Title Tags

Until the release of WordPress 4.1, each theme contained its own implementation of the <title> tag. This code often varied from theme to theme, making it difficult for plugins — for example SEO plugins — to customize the content of the title tags.

The new, recommended approach is to leverage the add_theme_support() function by declaring support for title-tag:

function theme_slug_setup() {
   add_theme_support( 'title-tag' );
}
add_action( 'after_setup_theme', 'theme_slug_setup' );

By declaring theme support, you indicate to WordPress that the title tag should be auto-generated. This is done using the private function _wp_render_title_tag(), which is hooked to wp_head. You can still use the wp_title filter to customize the output of the new auto-generated title tags.

Navigation and Pagination

While WordPress has included functions to generate navigation links between posts or pages of posts for a while, each theme used these functions with different markup and text. WordPress 4.1 provides template tags that output the entire navigation for you.

This allows theme developers to focus on the most important element: styling. Additionally, when using the default strings, these are automatically translated in your theme, because the translations for these strings are included in Core.

Post Navigation

The post navigation functions, the_post_navigation() and get_the_post_navigation(), output a set of links to the previous and next posts. These functions are used on single post views (like single.php).

These functions accept an array arguments:

  • prev_text: Text of the link to the previous post. Defaults to the post title.
  • next_text: Text of the link to the next post. Defaults to the post title.
  • screen_reader_text: Text meant for screen readers. Defaults to “Post navigation”.

Sample HTML output:

<nav class="navigation post-navigation" role="navigation">
    <h2 class="screen-reader-text">Post navigation</h2>
    <div class="nav-links">
        <div class="nav-previous"><a href="http://website.com/beautiful-sea" rel="prev">Beautiful Sea</a></div>
        <div class="nav-next"><a href="http://website.com/spring-landscape" rel="next">Spring Landscape</a></div>
    </div>
</nav>

Posts Navigation

The posts navigation functions, the_posts_navigation() and get_the_posts_navigation(), output a set of links to the previous and next pages of posts. These functions are used for post listings (like index.php) or archives (like archives.php).

These functions accept an array of arguments:

  • prev_text: Text of the link to the previous set of posts. Defaults to “Older posts”.
  • next_text: Text of the link to the next set of posts. Defaults to “Newer posts”.
  • screen_reader_text: Text meant for screen readers. Defaults to “Posts navigation”.

Sample HTML output:

<nav class="navigation posts-navigation" role="navigation">
    <h2 class="screen-reader-text">Posts navigation</h2>
    <div class="nav-links"><div class="nav-previous"><a href="http://website.com/page/3">Older posts</a></div><div class="nav-next"><a href="http://website.com/">Newer posts</a></div></div>
</nav>

Post Pagination

The posts pagination functions, the_posts_pagination() and get_the_posts_pagination(), output a set of page numbers with links to the previous and next pages of posts. These functions are used for post listings (like index.php) or archives (like archives.php).

These functions accept an array of arguments:

  • mid_size: How many page numbers to display to either side of the current page. Defaults to 1.
  • prev_text: Text of the link to the next set of posts. Defaults to “Previous”.
  • next_text: Text of the link to the next set of posts. Defaults to “Next”.
  • screen_reader_text: Text meant for screen readers. Defaults to “Posts navigation”.

Sample HTML output:

<nav class="navigation pagination" role="navigation">
    <h2 class="screen-reader-text">Posts navigation</h2>
    <div class="nav-links"><a class="prev page-numbers" href="http://website.com/page/3/">Previous</a>
        <a class="page-numbers" href="http://example.com/">1</a>
        <span class="page-numbers dots">…</span>
        <a class="page-numbers" href="http://example.com/page/3/">3</a>
        <span class="page-numbers current">4</span>
        <a class="page-numbers" href="http://example.com/page/5/">5</a>
        <a class="page-numbers" href="http://example.com/page/6/">6</a>
        <a class="next page-numbers" href="http://example.com/page/5/">Next</a>
   </div>
</nav>

Archives

Archives are an important feature in WordPress. By default, WordPress supports taxonomy (categories, tags and post formats), author, and date (year, month, day) archives.

Two of the default taxonomies, categories and tags, support archive descriptions. This feature allows users to add descriptions for each term in these taxonomies.

It has become a best practice among theme developers to display these descriptions on archive pages, along with a contextual archive title. WordPress 4.1 introduces two new template tags to help with this.

Archive titles

The the_archive_title() and get_the_archive_title() functions display the title of an archive, as in the term or the date, with a contextual text prefix. The prefix depends on the type of archive:

  • “Category: ” for category archives.
  • “Tag: ” for tag archives.
  • “Author: ” for author archives.
  • “Year: “, “Month: ” and “Day: ” for date archives.
  • “Asides: “, “Galleries: “, “Images: “, “Videos: “, “Quotes: “, “Links :”, “Statuses: “, “Audio: ” and “Chats: ” for post format archives.
  • “Archives: ” for custom post type archives.
  • Singular taxonomy name for custom taxonomy archives.

Theme developers that want to modify the default strings can use the get_the_archive_title filter to do so.

The the_archive_title() accepts two arguments, $before and $after, that can be used to add additional text or HTML before or after the archive title.

Archive description

The the_archive_description() and get_the_archive_description() functions output the description of a taxonomy. These functions work with categories and tags as well as custom taxonomies.

The the_archive_description() template tag accepts two arguments, $before and $after, that can be used to add additional text or HTML before or after the term description.

Screen Reader Text

When using these new template tags, you might be surprised by extra text being displayed.

This is because these functions include text that provide contextual information for screen readers. This is a very important accessibility feature and it does not impact your theme’s design, as you can remove these elements while still keeping them accessible for screen readers with the following styles for the .screen-reader-text class:

.screen-reader-text {
    clip: rect(1px, 1px, 1px, 1px);
    position: absolute !important;
    height: 1px;
    width: 1px;
    overflow: hidden;
}

Deprecated Admin Screens

WordPress 4.1 also deprecates the Background and Header screens in the admin. When users click on these links, they are redirected to the Customizer, where they can make changes with a visual preview of the results.

When adding theme support for the custom background feature, you will no longer have to implement callback functions for the admin-head-callback and admin-preview-callback arguments of add_theme_support( 'custom-background' ).

Want to know more?

You might agree these new functions are awesome, but you might be unsure how to use them. I’d encourage you to have a look at the _s (Underscores) starter theme on Github. It is up to date with all the new functions added in 4.1 and provides backwards compatibility for older versions of WordPress.  You can also look at the source code of Twenty Fifteen, which leverages all these new functions.

Happy theming!

Penscratch

Penscratch, a crisp new theme designed and developed by Caroline Moore, made its debut in the WordPress.org directory this week.

“Penscratch was inspired by a similar portfolio theme, Sketch, which I designed for visual art. I wanted a clean, minimalist theme with a similar look and feel, but tailored to writers.”

With support for Jetpack Site Logos and special styling for pull quotes, Penscratch is worth checking out.

Penscratch screenshot

banner-1544x500

Working with the Eventbrite API Plugin

Eventbrite and WordPress are the perfect fit, but until now, integrating the two has not been for the faint of heart. In early 2014, Eventbrite announced its new upcoming REST API, and this became the perfect opportunity to give theme developers an easy-to-use set of tools for working with Eventbrite events: the Eventbrite API plugin.

The plugin gives theme developers three ways to interact with the Eventbrite API:

  • Theme support
  • The Eventbrite_Query class
  • Helper functions

Theme Support

While the Eventbrite API plugin can display events in any theme, events look their best if the theme declares support and provides tailored templates. This simple process guarantees that events fit perfectly with the theme design, and adding support should take no more than ten minutes.

  1. Add a support declaration, hooked to after_setup_theme. There are no arguments, and usually this can be added to a theme’s existing setup function.
    function themeslug_setup() {
    
    	...
    
    	/**
    	 * Add theme support for the Eventbrite API plugin.
    	 * See: https://wordpress.org/plugins/eventbrite-api/
    	 */
    	add_theme_support( 'eventbrite' );
    }
    add_action( 'after_setup_theme', 'themeslug_setup' );
    
  2. Create an eventbrite folder in your theme, and copy over the plugin’s main template files (tmpl/eventbrite-index.php and tmpl/eventbrite-single.php).
  3. Compare the markup in eventbrite-index.php to your own index.php and adjust as necessary. Also, verify that your markup for archive titles matches the Eventbrite template’s page title. The Eventbrite templates don’t use template parts for the post markup, so you may need to compare with content.php or the like. Of course, there’s no reason you couldn’t add a content-eventbrite.php to your theme, if you prefer.
  4. Repeat step 3 with eventbrite-single.php and your own single template.

That’s it! If support is declared, the plugin will use those templates if they exist, or fall back to the plugin’s templates. To see some custom templates in action, check out any of the Twenty* default themes; their templates are included in the plugin.

Eventbrite integration with Twenty Fifteen.

Eventbrite integration with Twenty Fifteen.

The Eventbrite_Query Class

It was important to us that working with the Eventbrite API plugin should be a simple and familiar process for theme developers, with a low barrier to entry. With that in mind, we developed the Eventbrite_Query class, so fetching and displaying events is as simple as making a secondary loop (in fact, the class extends WP_Query). This allows for easy creation of special-purpose loops, widgets, creative page templates – any combination of events you want to display in a theme.

<?php
	// Get the next three unpublicized events for the Apollo Planetarium.
	$events = new Eventbrite_Query( apply_filters( 'eventbrite_query_args', array(
		'display_private' => true,
		'limit' => 3,
		'venue_id' => 6955925,
	) ) );

	if ( $events->have_posts() ) :
		while ( $events->have_posts() ) : $events->the_post(); ?>

There are a few things to keep in mind while working with Eventbrite_Query loops.

  • You can continue to use familiar template tags in event loops, such as the_post_thumbnail(), the_title(), the_content(), etc. They’ve simply been filtered to provide content from the current event.
  • For technical reasons, a few template tags need their Eventbrite equivalent, such as eventbrite_is_single() and eventbrite_edit_post_link().
  • Being a secondary loop, don’t forget to add wp_reset_postdata() at the end.
  • All of the plugin’s template tags are pluggable, and filters exist at various points for further customization.

Helper Functions

If you’re happy processing your own results, and just want an easy-to-use set of tools to handle the API requests, the included helper functions are for you. Each supported API endpoint has its own helper function, and these functions in turn use the Eventbrite_Manager class for the heavy lifting. Not only does this class make the actual API requests, but also handles validation and transients, so you can concentrate on results rather than mechanics.


The Eventbrite API plugin is developed on GitHub, and issues or questions can be posted there or in the forums. Additional info and documentation can be found here.

Along with the Eventbrite Services plugin, it’s never been easier or more fun to display events in your WordPress website. Let us know what you’re doing with Eventbrite, and tell us if there’s anything the Eventbrite API plugin can do to make your Eventbrite integrations easier for you!

The Eventbrite API plugin requires the Keyring plugin for managing OAuth2 authorization to Eventbrite. If you get stuck, check out our detailed instructions for getting connected to Eventbrite.

banner-1544x500

The Power of Eventbrite on WordPress

Eventbrite is the world’s premier event-management service, and we’re happy to announce two new ways to add Eventbrite events to your self-hosted WordPress site!

We’ve offered Eventbrite integration on WordPress.com for a while, with two dedicated themes. While this made getting your events on your WordPress site easier than ever, it wasn’t available to self-hosted users, and you were limited to only the two themes. Both of these issues are solved with new additions to the WordPress.org theme and plugin repositories.


The Eventbrite Multi theme by Voce Communications.

The Eventbrite Multi theme by Voce Communications.

Originally developed by Voce Communications, the Eventbrite themes that have been available on WordPress.com are now in the WordPress.org theme repository, and the plugin that powers them is also available for download. Together, the themes and the plugin provide full-featured Eventbrite integration for single and multiple events, including a calendar view and a widget. Huge thanks to Voce for continuing to support their work in the .org space!


Automattic has also developed an Eventbrite plugin, called Eventbrite API. This plugin is designed to work with any theme, with no explicit support required. It also provides a selection of simple tools that allow theme developers to work with events as easily as custom loops, making Eventbrite theme integrations more fun to build than ever. We’ll have a post next Monday demonstrating how to take advantage of this new plugin in your themes.

Eventbrite and WordPress are a perfect match, and we now have two great plugins for bringing them together. See you at the show!

Mastering the post_class() Function

The post_class() function is one of the many functions provided by WordPress to facilitate theme development. As the name suggests, the post_class() function outputs an HTML class attribute and sets its value to classes related to the post being output.

The correct way to use the function is to add it to the HTML tag that serves as the container for the post content:

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>

The post classes

The number and the name of the classes output by the post_class() function depends on the properties attached to a specific post. Here is an overview of the different possibilities and the contexts in which they are added.

hAtom compliance

WordPress respects the hAtom microformat. Therefore every post has an .hentry class added to it to respect the specification. This class is a great way to target both posts and pages in your CSS.

Post ID

An example of the post ID class might be .post-26. The number at the end of the class corresponds to the ID of this post in the database. As these IDs are unique, this class is a great way to target individual posts in your CSS. Something to keep in mind is that the post ID class starts with .post-, even for pages.

Post type

The post type identifies the type of content that is displayed. By default, WordPress includes posts and pages as content types. This information is output twice, once only the name of the post type (so .post and .page) and once prefixed with type- (so .type-post and .type-page).

When the theme displays a custom post type, the name of the post type that is output corresponds to the first parameter of the register_post_type() function. As an example the classes for the Portfolio Custom Post Type in Jetpack are .jetpack-portfolio and .type-jetpack-portfolio.

Post status

The post status determines how WordPress handles a specific post. Draft posts for example are not displayed on the front end, and private posts are only visible on the front end for users for administrator access. The status is added with status- as a prefix, so .status-published or .status-private for example.

Password protected posts

Posts that are only visible after having entered the post password receive the .post-password-required class.

Sticky

Posts that are marked as sticky receive the .sticky class, but only when they are displayed on the first page of the blog home. On single views or when they are displayed in other types of archives, this class won’t be added.

Post thumbnails

When the activate theme has declared support for post thumbnails, and the post has a featured image set, the .has-post-thumbnail class is added.

Post Formats

The format of the current post prepended with format-. The possible values for the format are aside, audio, chat, gallery, image, link, quote, status and video.

These classes are added independently of whether the theme has declared support for post formats or whether the theme supports the particular format in question. The determining factor for the output of these classes are whether the post type supports post formats. This means that these classes will get added to posts, but not to pages, as pages don’t support post formats out of the box.

Categories and Tags

The categories and tags associated to a particular post will be added with the category- and tag- prefix. The names of the categories and tags are turned into slugs, meaning that they are all lowercase, without special characters and with dashes instead of spaces.

Adding or removing post classes

The post_class() function accepts two optional arguments, $class and $post_id. It is possible to add classes by passing them either as a string or an array as the $class argument.

However, a better alternative is to use the post_class filter. By using a filter, all classes are added and removed in a single place, and the classes that are added aren’t dispersed among the templates files. Additionally this avoids duplication if you want to add classes in different contexts, and it makes it easier for child themes to remove or add their own classes.

Adding classes

Imagine that you want to add specific styles to posts that don’t have a comment yet. How can we do that?

function theme_slug_post_classes( $classes, $class, $post_id ) {
    if ( 0 == get_comments_number( $post_id ) ) {
        $classes[] = 'no-comments';
    }

    return $classes;
}
add_filter( 'post_class', 'theme_slug_post_classes', 10, 3 );

The first thing we need to do is add a custom function to our theme’s functions.php file. In this tutorial, we use a generic prefix; when using this code, please prefix the function correctly.

Our function accepts three parameters ($classes, $class, and $post_id), because these are the variables that WordPress passes through this filter:

  • $classes is an array of classes for the post.
  • $class is a comma separated list of additional classes that may have been added directly via the $class parameter of the post_class() function. If no classes were added, this variable is going to be an empty string.
  • $post_id is an integer and it corresponds to the unique ID of the post.

The $classes array is what we are going to use to add or remove classes. The other two variables provide context for this filter.

In this case, we can use the $post_id variable and pass it to get_comments_number(). This function will then return the number of comments for the post. If there are no comments, we add the .no-comments class to the $classes array.

At the end of the function, we return this array. It is important to do this even when you don’t modify the $classes array. If you don’t return any data or return malformed data, this will break the site.

As we are using the additional variables passed by the post_class filter, we need to add to arguments to the add_filter() call:

  • The 10 at the end corresponds to the priority with which the filter runs. This is the standard priority, and there is no need to change this.
  • The 3 corresponds to the number of variables passed. If you only pass two variables, you need to set this to 2. If you only pass one parameter, this argument and the previous argument can be omitted.

Removing classes

Removing classes works very much the same way. Imagine that we create a child theme for a theme that adds an extra .box class to every post, and we want to remove this.

function theme_slug_post_classes( $classes ) {
    $class_key = array_search( 'box', $classes );

    if ( false !== $class_key ) {
        unset( $classes[ $class_key ] );
    }

    return $classes;
}
add_filter( 'post_class', 'theme_slug_post_classes' );

As $classes is an array, we need to know the key of the array element containing the undesired .box class. This is because the unset() function needs this key in order to remove the corresponding value from the array.

So first we use the array_search() function to look for the box value in our $classes array. The return value of this function is then stored in the $class_key variable.

When the box value isn’t found, $class_key will be set to false, and the $classes array won’t be modified. But when the $class_key contains an integer, this condition will pass and the entry containing the box value will be removed from the $classes array.

In this example, we have removed an extra class. You should avoid removing classes added by WordPress itself, as plugins or user customizations might rely on these classes always being present.

Leveraging post classes in CSS

Now that we have seen how to interact with the post_class() function in PHP, we will look at a few quick tips for how this function can help you write better CSS.

  • Use the core provided classes: When you write your CSS, look at the HTML source code. Often WordPress provides you with the right classes that you can leverage in your CSS. In fact most themes can get by without modifying the post classes at all.
  • Use the body classes: The body_class() function works similar to post_class(). Together they can be used to target any post in any context. If you want to add specific styles to every post or page displayed on the search results page for example, all you need is the .search .hentry selector to target these entries.
  • Use custom parent selectors: When using secondary queries (via WP_Query) for example on a custom page template, developers often run into trouble because there is no easy way to only target the posts output by the secondary query. As with the previous tip, just adding a div element around the output of the loop will allow you style these posts by simply using the parent selector of the container element.

Conclusion

As we have seen post_class() is a very useful function and it will make styling your themes a lot easier if used properly. If you’ve got any questions, let me know in the comments.

Happy theming!