This talk will cover a few key “Aha” moments that you should have about the way WordPress works. We’ll talk about things like the template hierarchy, where WordPress content is stored, how posts and pages and custom post types are represented in the database, what folks are talking about when they talk about hooks and filters, and just generally review the “behind the scenes” mechanics of how WordPress works. We’ll also touch on a few “tricks of the trade” that you might not realize are out there, mainly version control, development environments, and Vagrant.

1. THINGS YOU SHOULD KNOW
ABOUT WORDPRESS
(but were always afraid to ask)
Power Users Track
WordCamp Raleigh 2014
Saturday, November 8th, 2014
Michael McNeill - @michaelrmcneill #wcraleigh

2. ABOUT ME
• Developer and Support Engineer in ITS Web Services at the University of
North Carolina at Chapel Hill, where I help to manage two HUGE multisite
networks that operate a total of almost 8,500+ sites.
• Owner and Developer at MRMcDEV, Inc. my personal consulting company.
• Co-Curator (Executive Director) of TEDxUNC, a non-profit organization
dedicated to bringing “Ideas Worth Spreading” to Carolina.
• I’ve been using WordPress for over 5 years now, and I use it for almost all my
client projects.
• I’ve worked on exciting and wide ranging projects, such as Black Enterprise
Magazine, Mackay Communications, WiredHoods, smallbiztechnology.com,
ALOHA, and MAXI Promotion and Records. I’ve also contracted for DRS
Technologies, the United States Department of the Defense, and numerous
other companies.
@michaelrmcneill
#wcraleigh

3. A QUICK ROADMAP…
1. The WordPress APIs - What they are, how to find them, and
how to use them.
2. The WordPress Template Hierarchy - What it is, which file
generates a certain type of page, and how to use it to your
advantage.
3. The WordPress Database - What is stored there, why it is
stored there, how is it stored there, and how should you
properly use the data inside it.
4. A few “tricks of the trade” - Version Control and Vagrant
@michaelrmcneill
#wcraleigh

4. THE WORDPRESS CODEX
@michaelrmcneill
#wcraleigh

5. BOOKMARK IT!
http://codex.wordpress.org
@michaelrmcneill
#wcraleigh

6. WHAT IS IT?
The WordPress Manual written for all users, Designers and
Developers alike.
@michaelrmcneill
#wcraleigh

7. USE IT & IMPROVE IT.
When you first have a question, go to the Codex first.
The Codex is a living document, and anyone with a WordPress.org account can
edit it and improve it. If you see something out of date, or flat out wrong, update it.
@michaelrmcneill
#wcraleigh

8. THE WORDPRESS APIs
@michaelrmcneill
#wcraleigh

9. WHAT’S AN API?
• APIs are Application Programming Interfaces.
• Think about it like this, APIs are basically a contract
between two things stating: "If you tell me this, I
will do this.”
@michaelrmcneill
#wcraleigh

10. WHAT DO THE WORDPRESS
APIs DO?
• They help you do things using tools that
WordPress gives you.
• That makes development EASIER!!
@michaelrmcneill
#wcraleigh

11. HOW DO I FIND THEM?
• Identify what you are trying to do.
• Then go to the ___________ and search for it.
• If that doesn’t work, try using Google, just
remember to cross-check against what the Codex
says.
@michaelrmcneill
#wcraleigh

12. HOW DO I USE THEM?
• The format is basically the same across all function
reference articles.
• There are 3 primary sections.
1. The description of the function.
2. The parameters the function wants/needs.
3. What values, if any, the function returns.
@michaelrmcneill
#wcraleigh

13. WORDPRESS PAGE LIFE CYCLE
• The WordPress page life cycle is a combination of
the events that take place from when a browser
requests a page to when the server returns the
rendered page to the browser.
• That sounds simple, but there are a lot of things
going on that get you the end result.
@michaelrmcneill
#wcraleigh

14. @michaelrmcneill
#wcraleigh

15. WORDPRESS HOOKS
• Hooks are extremely important to WordPress
developers.
• They enable us to literally hook into parts of the
WordPress page life cycle to retrieve, insert, and
modify data, and they allow us to take certain
actions behind the scenes, before a user sees what
is occurring.
@michaelrmcneill
#wcraleigh

16. WORDPRESS HOOKS
@michaelrmcneill
#wcraleigh
• Two Classifications
• Actions
• Actions are triggered by specific events that take place in WordPress,
such as publishing a post, activating a plugin, or loading an admin
screen.
• For a comprehensive list of actions, check this Codex article out:
http://codex.wordpress.org/Plugin_API/Action_Reference
• Filters
• Filters are functions that WordPress passes data through, that are
primarily responsible for intercepting, managing, and returning data,
before rendering or saving that data.
• For a pretty comprehensive list of filters, check this Codex article
out: http://codex.wordpress.org/Plugin_API/Filter_Reference

17. WORDPRESS HOOKS
• I’m sure you have the question, when should I use which
hook?
• Use actions when you want to add something to the
existing page such as stylesheets, JavaScript, or send an
email when an event has happened.
• Use filters when you want to manipulate data coming out
of the database prior to going to the browser, or coming
from the browser prior to going into the database.
@michaelrmcneill
#wcraleigh

18. THE WORDPRESS PAGE
TEMPLATE HIERARCHY
@michaelrmcneill
#wcraleigh

19. WHAT IS THE TEMPLATE
HIERARCHY?
WordPress templates fit together like the pieces of a
puzzle to generate the pages on your WordPress site.
Some templates (the header and footer templates
for example) are used on almost all pages, while
others are used only under specific conditions. The
template hierarchy decides what template file or files
WordPress will use to display a certain type of page.
@michaelrmcneill
#wcraleigh

20. @michaelrmcneill
#wcraleigh

21. LET’S LOOK AT THE BASICS
@michaelrmcneill
#wcraleigh

22. THE NEEDS OF A THEME
• To have a functioning, bare minimum theme you
need two things.
• style.css - A stylesheet.
• index.php - An index file that will render the
output of the page.
@michaelrmcneill
#wcraleigh

23. header.php
@michaelrmcneill
#wcraleigh

24. footer.php
@michaelrmcneill
#wcraleigh

25. single.php
@michaelrmcneill
#wcraleigh

26. sidebar.php
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27. SINGLE POST RULES
@michaelrmcneill
#wcraleigh
1. single-post.php
2. single.php
3. index.php

28. PAGE TEMPLATE RULES
1. Custom Template defined in WP Admin
2. page-<slug>.php
3. page-<id>.php
4. page.php
5. index.php
@michaelrmcneill
#wcraleigh

29. HOME PAGE TEMPLATE RULES
• front-page.php
• Settings > Reading
• Static Page
1. Follows the page template rules.
@michaelrmcneill
#wcraleigh
• Blog Page
1. home.php
2. index.php

30. SINGLE CUSTOM POST RULES
1. single-<posttype>.php
2. single.php
3. index.php
@michaelrmcneill
#wcraleigh

31. CUSTOM POST TYPE RULES
1. archive-<posttype>.php
2. archive.php
3. index.php
@michaelrmcneill
#wcraleigh

32. CATEGORY PAGES
1. category-<slug>.php
2. category-<id>.php
3. category.php
4. archive.php
5. index.php
@michaelrmcneill
#wcraleigh

33. TAG PAGES
@michaelrmcneill
#wcraleigh
1. tag-<slug>.php
2. tag-<id>.php
3. tag.php
4. archive.php
5. index.php

34. AUTHOR PAGES
1. author-<nicename>.php
2. author-<id>.php
3. author.php
4. archive.php
5. index.php
@michaelrmcneill
#wcraleigh

35. ATTACHMENT RULES
1. MIME-type.php (e.x. text.php, video.php,
image.php)
2. attachment.php
3. single_attachment.php
4. single.php
5. index.php
@michaelrmcneill
#wcraleigh

36. CODEX ARTICLE
http://codex.wordpress.org/Template_Hierarchy
INTERACTIVE WEBSITE!
http://wphierarchy.com/
@michaelrmcneill
#wcraleigh

37. WORDPRESS DATA
@michaelrmcneill
#wcraleigh

38. WORDPRESS DATA
• A WordPress website consists of three main
elements:
• The WordPress installation itself
• The contents of the wp-content directory which
includes the themes, plugins and uploads
• The database, where all the content is stored.
@michaelrmcneill
#wcraleigh

39. TYPES OF WORDPRESS
CONTENT
@michaelrmcneill
#wcraleigh
• posts
• pages
• custom post types
• attachments
• links
• menu items

40. ASSOCIATED DATA
(POSTMETA)
• categories
• tags
• custom taxonomies and terms
• post metadata
@michaelrmcneill
#wcraleigh

41. OTHER TYPES OF CONTENT
@michaelrmcneill
#wcraleigh
• widgets
• options
• users
• sites (for multisite)

42. @michaelrmcneill
#wcraleigh

43. A FEW NOTES…
• In the next few slides, I’m using the wp_ prefix by
default. You can change this (and you might have),
but the concepts are the same.
• A multisite installation will have some extra tables.
I haven't included those here as that's outside the
scope of this presentation.
@michaelrmcneill
#wcraleigh

44. THE WORDPRESS DATABASE
STRUCTURE
Most of the tables in the WordPress database are
linked to one or more other tables via a specific field.
This field is generally a unique ID for each record
such as a post_id.
@michaelrmcneill
#wcraleigh

45. THE WORDPRESS DATABASE
STRUCTURE
TABLE DATA STORED LINKED TO
wp_posts Posts, pages, attachments,
revisions and menu items
@michaelrmcneill
#wcraleigh
wp_postmeta
(using post_id)
wp_term_relationships
(using post_id)
wp_postmeta Post metadata wp_posts
(using post_id)

46. THE WORDPRESS DATABASE
STRUCTURE
TABLE DATA STORED LINKED TO
wp_comments Comments
@michaelrmcneill
#wcraleigh
wp_posts
(using post_id)
wp_commentmeta
(using comment_id)
wp_commentmeta Comment metadata wp_comments
(using comment_id)

47. THE WORDPRESS DATABASE
STRUCTURE
TABLE DATA STORED LINKED TO
wp_users Users
@michaelrmcneill
#wcraleigh
wp_posts
(using post_author)
wp_usermeta
(using user_id)
wp_usermeta Metadata for each user wp_users
(using user_id)

48. THE WORDPRESS DATABASE
STRUCTURE
TABLE DATA STORED LINKED TO
@michaelrmcneill
#wcraleigh
wp_links
(DEPRECATED!)
Information related to
Links
wp_term_relationships
(using link_id)
wp_options
Site settings and options
(set via the Settings
screens and via plugins and
themes) as well as widgets
None

49. THE WORDPRESS DATABASE
STRUCTURE
TABLE DATA STORED LINKED TO
wp_term_relationships Relationships between
posts and taxonomies
@michaelrmcneill
#wcraleigh
wp_posts
(using post_id)
wp_term_taxonomy
(using term_taxonomy_id)
wp_term_taxonomy Taxonomies (including
categories and tags)
wp_term_relationships
(using term_taxonomy_id)
wp_terms
Your categories and tags
and the terms assigned to
custom taxonomies
wp_term_taxonomy
(using term_id)

50. HOW TO USE THE
WORDPRESS DB?
WordPress defines a class called wpdb, which
contains a set of functions used to interact with a
database. Its purpose is to provide an easy to use
interface with the WordPress database.
@michaelrmcneill
#wcraleigh

51. $wpdb
Methods in the wpdb() class should not be called
directly. You should use the global $wpdb object
instead.
@michaelrmcneill
#wcraleigh

52. A LARGE WARNING
Any function that executes SQL queries, can be
vulnerable to SQL injection attacks. To prevent that,
you should escape all SQL. Make sure to review the
______ to double-check if the function you plan to
use escapes SQL for you or leaves it un-escaped!
@michaelrmcneill
#wcraleigh

53. TRICKS OF THE TRADE
@michaelrmcneill
#wcraleigh

54. VAGRANT AND VVV
http://vagrantup.com
https://github.com/Varying-Vagrant-Vagrants/VVV
A great tutorial: http://tangrufus.com/start-wordpress-
development-varying-vagrant-vagrants/
GIT AND GITHUB
Great intro guide and cheat sheet: http://
rogerdudler.github.io/git-guide/
GitHub: https://github.com
Deploy (Automated Deployment): https://
www.deployhq.com
@michaelrmcneill
#wcraleigh

55. QUESTIONS?
@michaelrmcneill
#wcraleigh