WordPress powers 20% of the internet

Accessibility & Extensibility

Core values

Posts

One table to rule them all

In WordPress, Everything is a Post*

* almost

Some built-in Post-Types:

• Post
• Page
• Attachment

Custom Post types let you make your own, e.g.:

• Portfolio Item
• Recipe
• Book

So what about metadata?

Post Meta

Key-value pairs containing data for posts. Can be managed by plugins or sometimes directly by administrators.

User Meta

The same, but for users instead of posts.

Caution:

Either might contain serialized data

Categories & tags

Categories & tags are examples of taxonomies

• You can make your own taxonomies
• Taxonomies can be hierarchical (categories) or not (tags)
• Any taxonomy can be associated with any post type
• Specific items within a taxonomy are called terms

Action Hooks

Almost event listeners

You can attach your own functions to action hooks

WordPress will run your code at the appropriate time

(e.g. upon initialization of the plugin)

Filters are like actions

But the callback takes and returns an argument

Plugins vs. Themes

Themes

Themes must contain an index.php and a style.css

Generally they should be used to provide style and not functionality, but any PHP and hooks are available for developers to use.

Plugins

Plugins have access to the same action hooks as themes, and typically contain functionality changes which might include default styles.

Plugins can also run code upon activation/deactivation

Wait, Just an index.php?

The WordPress Template Hierarchy

If a more specific template does not exist, WordPress will fallback

Sidebars and widgets

Sidebars are just buckets of widgets