Word press development paradigms, idiosyncrasies and other big

WordPress Development Paradigms, Idiosyncrasies and Other Big Words Tom Auger, Zeitguys inc. WordCamp Montreal, 2011

Introduction
About me:
Developer of standalone RIAs and large-scale server-side systems
Siebel integrator and database admin
Perl, PHP, JavaScript, ActionScript 3, SQL, Python, Java, etc.
Very much a “DIY Guy”

Surprising Learning Curve
Lots of files!
Confusing themes!
Arcane symbols!
sprintf(__('Something %s', 'domain'), 'weird');
Hooks everywhere!
add_action('init', 'obscure_func');
$var = apply_filters('obscure_filter');
Oh my!

The biggest challenge...
was learning what the topics were that I needed to learn about:
themes, templates, template parts and child themes
database access and the WP_Query in all its instances
action and filter hooks
WordPress object types: posts, taxonomies and meta data
i18n (l10n)
where to get reliable, high-level information and help

Meh.
Let's just go skunkworks.
I'm a seasoned dev after all...

DIY Approach = Low Level
Direct database access
In-place editing of plugin files
Forking theme files
In-place (gasp) editing of core files
Brute force JavaScript injection
Rolling your own sanitization and security measures

The Bad News
Unsustainable, fragile to updates
Non-scalable and highly one-off
Big security gaps
Missing out on built-in value-add intelligence
Re-inventing the wheel

Example: Adding <p> to content
The starting code:
$posts = get_posts(array( 'post_type' => 'my-custom-type' )); foreach($posts as $post){ echo '<div>'; echo $post->post_content; echo '<div>'; }

Option 1: Manually Wrap
Wait... what about multiple paragraphs? or enclosing block tags?
$posts = get_posts(array( 'post_type' => 'my-custom-type' )); foreach($posts as $post){ echo '<div>'; echo '<p>'.$post->post_content.'</p>; echo '<div>'; }

Option 1b: RegEx
Wheel, meet Tom. Tom, meet Wheel.
$blockElements = implode("|", array('ADDRESS','BLOCKQUOTE','CENTER','DIR','DIV','DL', etc...); $added_p = preg_replace( '/(?:s*<('.$blockElements.')(?:s+[^>]+s*)*>s*(.+?)s*</1>(?:r|n|$)*)|(?:s*(.+?)s*(?:r|n|$|(?=<(?:'.$blockElements.')>))+)/is','<p$1>$2$3</p1>n', $post->post_content);

But wait... doesn't WP already do this?
wpautop(), defined in formatting.php handles all the logic and edge cases
foreach($posts as $post){ echo '<div>'; echo wpautop($post->post_content); echo '<div>'; }

So what about the_content()?
Let's exploit those globals and template tags
foreach($posts as $post){ setup_postdata($post); echo '<div>'; the_content(); echo '<div>'; } wp_reset_postdata();

So how does the_content() do it?
IDE – site-wide search (or use phpxref or WPSeek)
In post-template.php:
function the_content($more_link_text = null, $stripteaser = 0) { $content = get_the_content($more_link_text, $stripteaser); $content = apply_filters('the_content', $content); $content = str_replace(']]>', ']]>', $content); echo $content; }

Keep following the White Rabbit
Search for "the_content" within default-filters.php
It runs the following functions:
capital_P_dangit
wptexturize
convert_smilies
convert_chars
wpautop
shortcode_unautop
prepend_attachment
That's a lot of value add!

I want all that other good stuff, too!
Leverage all those the_content methods
foreach($posts as $post){ echo '<div>'; echo apply_filters( 'the_content', $page->post_content ); echo '<div>'; }

The lesson thus far
TMTOWTDI, but not all ways are equal
Use the method that:
is the most abstracted (high level)
requires the least amount of additional code
encapsulates the most value-added intelligence

“ Whenever you're going to write a code block that seems to be quite generic and common, check first if there's a WP function that can do it for you.” – Ozh Richard, de facto WP Plugin expert

Big Words
Paradigm: a model or pattern that defines a way of thinking or working with a tool
Idiosyncrasy: an unusual, distinctive and recognizable trait or pattern
Idiom: a form of expression, natural to a language or context

WordPress Paradigms and Patterns
Plugins
Templates
Hooks
Post Types and Taxonomies

WordPress Idioms
The Loop and the Query
Template tags (and get_)

WordPress Idiosyncrasies
$wpdb
wp_enqueue_script()
No TIME!! (part deux?)
wp_kses(), esc_attr()
body_class(), post_class(), comment_class()

Paradigm: Plugins
Often confused with Widgets
Nothing more than a distributableway to inject code at the start of the loading / execution cycle
Not to be confused with pluggable functions
<?php /* Plugin Name: Name Of The Plugin */ ?>

Paradigm: Themes and Templates

Themes
Control visual look-and-feel of a site
Require at minimum only index.php and style.css
But wait, there's more, with functions.php:
Widgets
Admin options
Changes to core behaviour

Child Themes
Best way to customize a theme for a specific client application
Clever overloading scheme
Leverage existing intelligence
%> wp-content/themes/my-child-theme/style.css /* Theme Name: Twenty Ten Child Theme Template: twentyten */ @import url('../twentyten/style.css');

Template Files
PHP files, loaded contextually based on Query string
Overloaded using a strict Template Hierarchy
Follows conditional hierarchy

Template Parts
Breaks down template hierarchy to custom level of granularity
Code reuse design pattern
Allows multiple templates to share sections
Eg: events-by-date.php, events-by-category.php, all-events.php
Note: local vars lose scope (uses "get")
include(locate_template('template-part')); get_template_part('template', 'part');

Page Templates
Templates that can be admin-applied to Pages (not posts)
<?php /* Template Name: 3 Column */ ?>

Post Formats
Standardized contributor-assignable taxonomy for posts
Meant to be consistent across all blogs
aside, chat, gallery, link, image, quote, status, video, audio
<?php get_template_part( 'format', get_post_format()); ?>

Paradigm: Hooks, Actions and Filters

“ WordPress action hooks are a means of providing a way for other developers to insert their own code in specific locations within your code, in order to change or expand the functionality of your code.” – Nathan Rice
http://www.nathanrice.net/blog/an-introduction-to-wordpress-action-hooks/

Hooks
Spiritually related to GoF's Template Method Design Pattern
Alternative extension method to subclassing
Developers create hooks wherever they think other devs may wish to extend their code
Documented under PluginAPI, but you will encounter them sooner than that

Actions vs. Filters
Actions inject code into a workflow
Filters take a variable, modify it and return the same type
// set up action hook do_action('hook-name'); // set up filter hook $variable = apply_filters('filter-name', $variable);

Leveraging Action Hooks
Use an action hook to do something at a specific point in the execution cycle
Multiple sources can register for a single action hook
add_action('init', 'stuff_to_do_at_init');

General Execution Order
muplugins_loaded
plugins_loaded
sanitize_comment_cookies
setup_theme
load_textdomain
after_setup_theme
auth_cookie_malformed
set_current_user
init
widgets_init
register_sidebar
wp_register_sidebar_widget
wp_loaded
parse_request*
send_headers*
parse_query*
pre_get_posts*
posts_selection
wp*
template_redirect
get_header
wp_head
wp_enqueue_scripts
wp_print_styles
wp_print_scripts
get_template_part_loop
loop_start*
the_post*
loop_end*
get_sidebar
dynamic_sidebar
get_search_form
wp_meta
get_footer
twentyten_credits
wp_footer
wp_print_footer_scripts
shutdown
http://codex.wordpress.org/Plugin_API/Action_Reference#Actions_Run_During_a_Typical_Request

Action examples add_action('init', 'register_my_custom_post'); add_action('init', 'register_my_custom_taxonomy'); add_action('widgets_init', 'register_my_widget'); add_action('wp_enqueue_scripts', 'add_my_js_libs'); add_action('save_post', 'save_my_custom_meta');

Leveraging Filter Hooks
Use a filter hook to modify output or an internal variable
add_filter('the_content', 'change_content'); function change_content($content){ $content = 'All your base are belong to us!!!'; return $content; }

Priority and Parameters
add_filter can take two additional arguments: $priority and $num_args
add_filter('contextual_help', 'my_help', 10, 3); function my_help($text, $screen_id, $screen){ if ($screen_id == 'edit-my_custom_post_type'){ $text = '<p>You are on your own pal</p>'; } return $text; }

Filter Examples add_filter( 'excerpt_more', 'custom_more' ); add_filter( 'excerpt_length', 'my_length', 999 ); function my_length($length){ return 6; // six is average, right? }

Existing Filters and Actions
WordPress already registers filters and actions
Find them in wp-includes/default-filters.php
remove_filter($tag, $function, $priority)
remove_action() is an alias

So How Do I Find Them?
Partial lists in the codex:
codex.wordpress.org/Plugin_API/Filter_Reference
codex.wordpress.org/Plugin_API/Action_Reference
Use a good IDE like Eclipse/PHP, Aptana, NetBeans, PHPStorm etc... and search for:
do_action(), and do_action_ref_array()
apply_filters(), and apply_filters_ref_array()
http://adambrown.info/p/wp_hooks

Good Citizenship
Add your own action and filter hooks wherever it may be appropriate:
things a dev may wish to override but you don't want to expose to an Admin user
default values (max/min limits etc)
logical spots for extension
Example: zg-event-query (filter)
For the love of Pete, document it!

Idiom: The Loop and The Query

Getting Your Content: "The Loop"
One "The Loop" per page
Sets globals (eg: $post)
Drives all template tags (eg: the_content())
Driven by "the query": the request string
Affects conditional tags
Can be supplanted by query_posts()

Secondary Loops
Used in widgets and sidebars, sub-content and related content
Must be careful not to clobber globals and affect the main Loop
Leverage get_posts() or get_pages() for inobtrusive secondary loops
Or get dirty with WP_Query class
Either way, be sure to read Codex WP_Query

Suspicious Stuff
Leverage template tags in secondary loops by:
using the_post() method on WP_Query instance
or setup_postdata() on a $post object
$the_query = new WP_Query( $args ); while ( $the_query->have_posts() ){ $the_query->the_post(); the_title(); } wp_reset_postdata();

Template Tags and get_
Template tags
Used exclusively within The Loop
Always echo their results
Rarely (?) take arguments (always working on the global $post object)
get_
Most template tags have a get_ equivalent
Does not echo result
Usually takes the ID of a post as argument

Template Tag vs. get_
Use Template Tag when:
you're in The Loop!
Use get_ when:
you want the value, not the echo
you're not in The Loop
you are in the loop but want a related item (eg: attachment)

Idiosyncrasy: $wpdb

wpdb Class
Instantiated once and globalized in $wpdb
Provides API to low-level DB calls
$wpdb->query()
$wpdb->get_results()
$wpdb->get_var()

Example: Events
Custom post type "event"
Categorized by taxonomy "event-type"
Event start_date stored in meta
Let's select: all 'speaking' events with a start date of '2011-07-09'

Pure SQL select * from wp_posts join wp_term_relationships on ID = object_id join wp_term_taxonomy on wp_term_taxonomy.term_taxonomy_id = wp_term_relationships.term_taxonomy_id and taxonomy = 'event-type' join wp_terms on wp_term_taxonomy.term_id = wp_terms.term_id and wp_terms.slug = 'speaking' join wp_postmeta on wp_postmeta.post_id = ID and meta_key = 'event-date' and meta_value = '2011-07-09' where post_type = 'event' and post_status = 'published'

More Properer SQL select * from wp_posts as P join wp_term_relationships TR_EVENT on P .ID = TR_EVENT .object_id join wp_term_taxonomy TT_EVENT on TT_EVENT .term_taxonomy_id = TR_EVENT .term_taxonomy_id TT_EVENT .taxonomy = 'event-type' join wp_terms T_EVENT on TT_EVENT .term_id = T_EVENT .term_id and T_EVENT .slug = 'speaking' join wp_postmeta M_DATE on M_DATE .post_id = P.ID and M_DATE .meta_key = 'event-date' and M_DATE .meta_value = '2011-07-09' where P .post_type = 'event' and P .post_status = 'published'

Don't Use Table Names! select * from {$wpdb->posts} P join {$wpdb->term_relationships} TR_EVENT on P.ID = TR_EVENT.object_id join {$wpdb->term_taxonomy} TT_EVENT on TT_EVENT.term_taxonomy_id = TR_EVENT.term_taxonomy_id TT_EVENT.taxonomy = 'event-type' join {$wpdb->terms} T_EVENT on TT_EVENT.term_id =T_EVENT.term_id and T_EVENT.slug = 'speaking' join {$wpdb->postmeta} M_DATE on M_DATE.post_id = P.ID and M_DATE.meta_key = 'event-date' and M_DATE.meta_value = '2011-07-09' where P.post_type = 'event' and P.post_status = 'published'

More Saferer Query $wpdb->prepare ("select * from {$wpdb->posts} P join {$wpdb->term_relationships} TR_EVENT on P.ID = TR_EVENT.object_id join {$wpdb->term_taxonomy} TT_EVENT on TT_EVENT.term_taxonomy_id = TR_EVENT.term_taxonomy_id TT_EVENT.taxonomy = 'event-type' join {$wpdb->terms} T_EVENT on TT_EVENT.term_id =T_EVENT.term_id and T_EVENT.slug = %s join {$wpdb->postmeta} M_DATE on M_DATE.post_id = P.ID and M_DATE.meta_key = 'event-date' and M_DATE.meta_value = %s where P.post_type = 'event' and P.post_status = 'published'", 'speaking', '2011-07-09' );

But, Whenever We Can... get_posts(array( 'post_type' => 'event', 'tax_query' => array(array( 'taxonomy' => 'event-type', 'field' => 'slug' 'terms' => 'speaking' )), 'meta_query' => array(array( 'key' => 'event-date', 'value' => $todays_date )) ));

Use Built-Ins Whenever You Can
Take advantage of cacheing and optimization
Future-proof code
Chances are, there's a function or method to do what you want
Look in Codex under WP_Query
Look in source under query.php, post.php, category.php, taxonomy.php

Idiosyncrasy: wp_enqueue_script

We Love jQuery
(Don't)
Jump into header.php
Add <script src="my-jquery-min.js"></script>
(Don't)
add_action('wp_head', 'add_my_jquery');

Enqueue = The Canadian Way, eh?
DO
add_action('wp_enqueue_scripts', 'add_my_scripts');
function add_my_scripts(){
wp_enqueue_scripts('jquery-ui-core',
get_stylesheet_directory_uri() . '/script',
array('jquery'),
'1.8.14',
false // in-header
);
}
add_action('admin_enqueue_scripts', 'add_admin_scripts'); // careful here...

No One Likes Conflict
jQuery runs in "no-conflict" mode...
jQuery(document).ready(function($) { $('#mydiv').css({color:'red', border:'2px solid red'}); }); (function($) { var test = "hello, world!"; function testMe(){ alert(test); } $(document).ready(testMe); })(jQuery);

Resources and Forums
Documentation:
Codex (of course)
Google: "wordpress add_action"
Adam Brown
WPSeek, phpxref
Your own IDE
Help:
wordpress.org/support (yeah, not really...)
www.experts-exchange.com
http://www.experts-exchange.com/Web_Development/Blogs/WordPress /
wordpress.stackexchange.com

Thanks! www.tomauger.com www.zeitguys.com @TomAuger

Other Stuff for more time

Paradigm: Post Types and Taxonomies

Posts
Posts are the atomic element for all WordPress content
"actual" posts
pages
comments
attachments
drafts and revisions
custom post types

Taxonomies
Taxonomies are the relational device that group posts together.
categories,
tags,
nav menus
post formats?
custom taxonomies
Groupings that are shared by different items

What About Meta?
Use meta for discrete, non-grouping data, unique to the content item (eg: price)
Sortables (eg: year)
Groups that are not meaningfully shared (eg: Otto's TV show seasons across different shows)

Custom Post vs. Custom Tax
Use Custom Post for content that:
should not appear in your feed
represents a distinct type of "content"
is always associated with a set of metadata
may require a customized input form
needs a separate capability / access
needs its own private taxonomy
Examples: products, events, albums

Custom Post vs. Custom Tax
Use a custom taxonomy when:
You want additional ways to group items together
You want a way to filter out a set of items
You want a new metabox
Eg: colour, software posts, manufacturers

Word press development paradigms, idiosyncrasies and other big

by TomAuger

Accessibility

Categories

Upload Details

Usage Rights

2 Embeds 4

Statistics

Word press development paradigms, idiosyncrasies and other big Presentation Transcript

http://lanyrd.com	3
url_unknown	1