Are there any books, websites or lectures that explain the built-in WordPress classes? I would really like to learn how WordPress works internally.

I've dug up the core files on trac and even went through the class reference on codex but yet I find it difficult to learn this way.

I know this is not a place to be asking for resources but everywhere I search the results are theme/plugin tutorials. I really want to understand the internal working of WordPress, can anyone give me pointers to go ahead with this? My PHP skills are just above intermediate


2 Answers 2


https://developer.wordpress.org/reference/ is sometimes more useful or other links on that page like Getting Started with WordPress. But you're better off with running Query Monitor to see what is happening on each page then looking up the concepts individually. I don't think anyone learns WP in a day. I think they typically focus on a single topic at a time after referencing existing themes and plugins. GenerateWP can jumpstart you in a better direction as well by creating well-form code.

Part of the journey to learn is being able to see what is happening when you test new ideas. I highly recommend the tools below.

Good Stack Exchange Answers;

Interactive diagram for the template hierachy

  • 1
    great share and great pointers
    – prosti
    Commented Oct 17, 2016 at 9:24
  • Was this answer helpful to your question?
    – jgraup
    Commented Nov 28, 2016 at 13:45

I suggest you the following approach. You download WordPress. Use the Text editor with the search feature, like Atom-editor, or Sublime and read the comments. You may get the idea about what classes exists, and how they came in to WordPress.

 * Requests for PHP
 * Inspired by Requests for Python.
 * Based on concepts from SimplePie_File, RequestCore and WP_Http.
 * @package Requests
class Requests {

This one came into WordPress from the author that also works on SimplePie project and works on REST API.

Find the author, watch the videos, and you will soon know more than you can imagine.

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