Intro to WordPress theme development

THEME DEVELOPMENT
an introduction to the basics of theming with WordPress

About me

• Name: Thad Allender

• Web: ThadAllender.com & GraphPaperPress.com

• Twitter: @thadallender

• Email: thadallender@gmail.com

Poll

•Blogger?
•Designer?
•Developer?

Anatomy of a WordPress theme

• WordPress Themes are files that work together to create the
design and functionality of a WordPress site

• http://codex.wordpress.org/Theme_Development


• Themes live in /wp-content/themes/

• Themes include stylesheets, template & functions files, images,
javascripts

• style.css – The main stylesheet. This must be included with your theme.

• index.php – The main template. If your theme provides its own templates, index.php must be present.

• comments.php – The comments template. If not present, wp-comments.php is used.

• single.php – The single post template. Used when a single post is queried. For this and all other query templates, index.php is used if the query template is not present.

• page.php – The page template. Used when a page is queried.

• category.php – The category template. Used when a category is queried.

• author.php – The author template. Used when an author is queried.

• date.php – The date/time template. Used when a date or time is queried. Year, month, day, hour, minute, second.

• archive.php – The archive template. Used when a category, author, or date is queried. Note that this template will be overridden by category.php, author.php, and date.php for their
respective query types.

• search.php – The search template. Used when a search is performed.

• 404.php – The 404 Not Found template. Used when WordPress cannot find a post that matches the query.

/*
style.css
Theme Name: Twenty Ten

Theme URI: http://wordpress.org/

Description: The theme description.

Author: the WordPress team

Version: 1.3-alpha

Tags: black, two-columns, fixed-width, custom-header

*/

index.php
<?php get_header(); ?>

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

! <h1><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent link
to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h1>

! <?php the_content(); ?>

<?php endwhile; else: ?>

! <p><?php _e('Sorry, no posts matched your criteria.'); ?></p>

<?php endif; ?>

<?php get_footer(); ?>

Page Structure

• Made up of three basic building blocks: a header, the content,
and a footer. Sidebars add additional functionality.

header.php

• Called with: get_header()

• Includes everything that comes before and including the <body>,
meta info, scripts, styles, wp_head, site name, navigation.

index.php

• Typically displays content from the loop (title, content, etc.)

• Calls get_header(), get_sidebar(), get_footer

footer.php

• Called with: get_footer()

• Can include credits, copyright info, wp_footer hook.

sidebar.php

• Called with get_sidebar()

• Adds contextual site info. Typically includes widgets.

Template Hierarchy

• The order in which WordPress template files are chosen

• http://codex.wordpress.org/Template_Hierarchy

Home Page Display

1.home.php

2.index.php

Single Post Display

1.single-{post_type}.php - If the post_type were videos,
WordPress would look for single-videos.php.

2.single.php

3.index.php

Page Display
1.custom template - Where custom template is the Page Template
assigned to the Page.

2.page-{slug}.php - If the page slug is recent-news, WordPress will
look to use page-recent-news.php

3.page-{id}.php - If the page ID is 6, WordPress will look to use
page-6.php

4.page.php

5.index.php

Category Display
1.category-{slug}.php - If the category's slug were news,
WordPress would look for category-news.php

2.category-{id}.php - If the category's ID were 6, WordPress
would look for category-6.php

3.category.php

4.archive.php

5.index.php

Tag Display
1.tag-{slug}.php - If the tag's slug were sometag, WordPress would
look for tag-sometag.php

2.tag-{id}.php - If the tag's ID were 6, WordPress would look for
tag-6.php

3.tag.php

4.archive.php

5.index.php

Custom Post Type Display

1.'has_archive' => true

2.archive-{$post_type}.php

3.archive.php

4.index.php

Author Display
1.author-{nicename}.php - If the author's nice name were rami,
WordPress would look for author-rami.php.

2.author-{id}.php - If the author's ID were 6, WordPress would
look for author-6.php.

3.author.php

4.archive.php

5.index.php

Date Display

1.date.php

2.archive.php

3.index.php

Search Display

1.search.php

2.index.php

404 (Not Found) Display

1.404.php

2.index.php

Attachment Display

1.MIME_type.php - it can be any MIME type (image.php,
video.php, audio.php, application.php or any other).

2.attachment.php

3.single.php

4.index.php

Development Environment

• Mamp (Mac) or Wamp (PC)

• For running WordPress locally (Apache, PHP, MySQL)

• http://www.mamp.info/en/index.html

• http://www.wampserver.com/en/

• http://codex.wordpress.org/
Installing_WordPress_Locally_on_Your_Mac_With_MAMP

Version Control

• Simplifies collaborative development, comparing, releasing

• SVN - http://subversion.tigris.org/

• GIT - http://git-scm.com/

The Loop

• Displays each of your posts

• http://codex.wordpress.org/The_Loop

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

....add template tags here....

<?php endwhile; else: ?>

<p><?php _e('Sorry, no posts matched your criteria.'); ?></p>

<?php endif; ?>

Query Posts

• query_posts(‘cat=1&showposts=5’)

• http://codex.wordpress.org/Function_Reference/query_posts

query_posts()
• Use it to control which posts show up in The Loop.

• Display only a single post on your homepage (a single Page can be done via
Settings -> Reading).

• Show all posts from a particular time period.

• Show the latest post (only) on the front page.

• Change how posts are ordered.

• Show posts from only one category.

• Exclude one or more categories.

query_posts()
<?php

query_posts('posts_per_page=5');

if ( have_posts() ) : while ( have_posts() ) : the_post();

..

endwhile; else:

..

endif;

wp_reset_query();

?>

query_posts()

The query_posts function is intended to be used to
modify the main page Loop only. It is not intended
as a means to create secondary Loops on the page. If
you want to create separate Loops outside of the
main one, you should use get_posts() instead.

Get Posts

• get_posts(‘cat=1&numberposts=3’)

• http://codex.wordpress.org/Template_Tags/get_posts

<ul> get_posts()
<?php

global $post;

$myposts = get_posts('posts_per_page=5&offset=1&category=1');

foreach($myposts as $post) :

setup_postdata($post);

?>

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

<?php endforeach; ?>

</ul>

Template Tags

• Used to display dynamic information about your site

• http://codex.wordpress.org/Template_Tags

Include Tags

Template include tags are used within one
template ﬁle (for example index.php) to
execute the HTML and PHP found in another
template ﬁle (for example header.php).

• get_header()

• http://codex.wordpress.org/Include_Tags

Include Tags
• get_header() - includes header.php or header-{name}.php

• get_footer() - includes footer.php or footer-{name}.php

• get_sidebar() - includes sidebar.php or sidebar-{name}.php

• get_template_part() - includes {slug}.php or {slug}-{name}.php

• get_search_form() - includes searchform.php

• comments_template() - includes comments.php or wp-includes/
theme-compat/comments.php

Body Class

• body_class()

• http://codex.wordpress.org/Function_Reference/body_class

body_class()

Helps theme authors style more effectively
with CSS by applying different classes to the
body element

• <body <?php body_class(); ?>

• <body class="archive category category-daily-photo">

Post Class

• post_class()

• http://codex.wordpress.org/Function_Reference/post_class

post_class()

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

<article id="post-1167" class="post-1167 post type-post
hentry category-daily-photo tag-dc tag-georgetown tag-
washington">

Get Template Part

• get_template_part()

• http://codex.wordpress.org/Function_Reference/
get_template_part

get_template_part()
• get_template_part( 'loop', 'index' );

• Looks for a file named ‘loop-index.php’ in the current theme

• If not found, looks for ‘loop.php’

• If this is a child theme, and neither of those templates exist, looks
in the parent theme.

• Each of the major templates (‘archive.php’, ‘author.php’,
‘category.php’, etc) makes a call similar to this, looking for a loop
template specific to the appropriate view.

Post Formats

• has_post_format()

• http://codex.wordpress.org/Post_Formats

while ( the_loop() ):

if ( has_post_format( 'gallery' ) ) :

// big block of HTML to format a gallery post

elseif ( has_post_format( 'video' ) ) :

// big block of similar HTML to format a video post

elseif ( has_post_format( 'image' ) ) :

// big block of similar HTML to format an image post

elseif ( has_post_format( 'aside' ) ) :

// big block of similar HTML to format an aside

else :

// big block of similar HTML to format other posts

endif;

endwhile;

get_template_part() and
get_post_format()

while ( the_loop() ):

get_template_part( 'format', get_post_format() );

endwhile;

get_template_part() and
get_post_format()

If the current post has post format ‘Link’, then we
look for a file named ‘format-link.php’. If the current
post has format ‘Aside’, we look for ‘format-
aside.php’, if it’s a Quote, ‘format-quote.php’,
regular posts look for ‘format-standard.php’, and
failing all else, we use plain old ‘format.php’.

Enqueue Javascripts

• wp_enqueue_script()

wp_enqueue_script

wp_enqueue_script()
<?php

function my_init_method() {

wp_deregister_script( 'jquery' );

wp_register_script( 'jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js');

wp_enqueue_script( 'jquery' );

}

add_action('init', 'my_init_method');

?>

add_theme_support()

add_theme_support

Conditional Tags

Used in Template files to change what
content is displayed and how that content is
displayed on a particular page depending on
what conditions that page matches

• http://codex.wordpress.org/Conditional_Tags

Conditional Tags
if (is_home) {
echo ‘This is home!’;
} else {
echo ‘No home!’;
}

Confused? Comment your code

• 

• // PHP comment goes here

Child Themes

• Inherits the functionality of another theme, called the parent
theme, and allows you to modify, or add to, the functionality of
that parent theme

• http://codex.wordpress.org/Child_Themes

Child themes: style.css
/*

Theme Name: TwentyTen Child

Template: twentyten

Version: 1.0

Author: Thad Allender

*/

@import url("../twentyten/style.css");

Child themes: functions.php

The functions.php of a child theme does not override
its counterpart from the parent. Instead, it is loaded in
addition to the parent’s functions.php. (Specifically,
it is loaded right before the parent’s file.)

Child Themes: Including files

TEMPLATEPATH - returns the path to the template files of a theme

STYLESHEETPATH - returns the path to the template files of the child theme

require_once( STYLESHEETPATH . '/path/to/file/in/child/theme.php' );

Child themes: File Overrides

•All other template files override their namesakes
from the parent.

•Example: twentyten-child/single.php overrides
twentyten/single.php

•This holds true to all templates in the WordPress
hierarchy and new templates introduced using
get_template_part()

Child Themes: Approaches
Because a child theme’s functions.php is loaded first, you can make the user
functions of your theme pluggable—that is, replaceable by a child theme—by
declaring them conditionally in the parent.

if (!function_exists('my_index_loop')) {

function my_index_loop() {

// Do something.

}

}

In that way, a child theme can replace a PHP function of the parent by simply
declaring it again.

Child Themes: Hooks

Enables you to add, remove or change code in supporting parent
themes

http://themeshaper.com/action-hooks-wordpress-child-
themes/

Theme Testing Tools
• wp-config.php: define('WP_DEBUG', true);

• http://wordpress.org/extend/plugins/theme-check/

• http://wordpress.org/extend/plugins/log-deprecated-notices/

• http://codex.wordpress.org/
Theme_Development#Theme_Testing_Process

• Unit test your theme:
http://codex.wordpress.org/Theme_Unit_Test

Intro to WordPress theme development

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