- Searching through core files as reference
- Working with the WordPress Codex
- Navigating the WordPress Code Reference
- Understanding inline documentation
To understand how to extend WordPress properly, you must first learn how the core of WordPress functions. This will help you learn what tools are available in the WordPress core to make your life easier. WordPress handles most of the tedious coding and logic problems for you.
The WordPress core is the best resource for learning how WordPress works. The beauty of open source software is you have all of the code at your disposal. If you are ever unsure how a certain aspect of WordPress functions, just start digging into the code! The answers are all there; it’s just a matter of finding and understanding them.
WHAT’S IN THE CORE?
The WordPress core is powered by a set of files that are part of the original WordPress software download. These are required “core” files that WordPress needs to function properly. The core files are expected to change only when you upgrade WordPress to a newer version.
The core does not include your custom files for plugins, themes, database settings, the
.htaccess file, and so on. The core also does not include any media you have uploaded to WordPress. Basically, any files added to WordPress after installation are considered outside of the core.
- Posts, pages, and custom content—Creating, storing, retrieving, and interacting with the majority of your content in WordPress. The discussion of the loop that controls content display and ordering in Chapter 5 relies heavily on these functions.
- Post types, taxonomies, and metadata—Everything from custom post types, tags, and categories to user-created taxonomies. The data models used are explored in Chapter 7.
- Themes—Supporting functions for WordPress themes. Theme development and its relationship to these functions are discussed in Chapter 9.
- Actions, filters, and plugins—Framework for extending WordPress through plugins, covered in more detail in Chapter 8.
- Users and authors—Creating and managing access control to your site, and key to the security and enterprise use topics in Chapters 12 and 15.
- Feeds, formatting, and comments—These are discussed as needed throughout the book.
This tutorial digs into these files as you explore the WordPress core files. Think of this tutorial as your guidebook to the “how” of exploring the WordPress core; it is a field guide companion to the WordPress Codex documentation for user-contributed discussion and explanation. It’s also imperative to be comfortable browsing and searching the core to complement the functional introduction provided here. An exhaustive list of every WordPress function is not included here, both because the list changes and evolves as the WordPress core undergoes continuous development, and because the goal here is to convey developer and deployer expertise and not to summarize the Codex.
WordPress comes packaged with two plugins: Akismet and Hello Dolly. These two plugins exist in your plugins directory inside
wp-content. Even though these two plugins are a part of the WordPress core file package download, they are not considered core functionality because they must be activated to function and can easily be removed.
WordPress also comes packaged with three core themes: Twenty Twelve, Twenty Thirteen, and Twenty Fourteen. Twenty Fourteen is the default theme on a fresh installation of WordPress. As with the included plugins, these theme files are not considered core functionality because they can easily be replaced with any theme that you want to use on your website.
USING THE CORE AS A REFERENCE
Using the WordPress core as a reference is a quick and easy way to learn about various functionality in WordPress. Understanding how to navigate through the WordPress core files can help you find answers to your questions when developing for WordPress.
To use the WordPress core as a reference, you need to understand what to expect in the core files. Most WordPress core files contain documentation in the form of code comments. Typically, a code comment is displayed in the header of the file and gives an overall summary of the core file you are viewing.
To see this first-hand, open the
wp-login.php file located in the root directory of WordPress. You’ll notice the top of the file has a header comment describing the file’s function:
/** * WordPress User Page * * Handles authentication, registering, resetting passwords, forgot password, * and other user handling. * * @package WordPress */
All core files, other than images, can be viewed using a text editor program. Depending on your default program settings, you may need to open up your text editor first and then open the file rather than just opening up the file directly. It’s also helpful to use a text editor that has syntax highlighting, meaning PHP syntax would be highlighted to help you read the code easier.
There is a full list of compatible text editors on the WordPress.org Codex at