WordPress is the most popular self‐hosted
website software in use today. It is available as an open source project, licensed under the GPL, and

is built largely on top of the MySQL database and PHP programming language. Any server envi-
ronment that supports that simple combination can run WordPress, making it remarkably portable

as well as simple to install and operate. You don’t need to be a systems administrator, developer,
HTML expert, or design aesthete to use WordPress. On the other hand, because WordPress has
been developed using a powerful set of Internet standard platforms, it can be extended and tailored
for a wide variety of applications. WordPress is the publishing mechanism underneath millions of
individual blog voices and the engine that powers high‐volume, high‐profi le sites such as CNN’s
websites and blogs. It was designed for anyone comfortable navigating a browser, but is accessible to
web designers and developers as well.
Given that range of applications and capabilities, it can prove hard to know where to start if you
want to make use of the power of WordPress for your specifi c purposes. Should you fi rst study the

database models and relationships of content and metadata, or the presentation mechanics that gen-
erate the HTML output? This book was designed for readers to develop a knowledge of WordPress

from the inside out, focusing on the internal structure and fl ow of the core code as well as the data
model on which that code operates. Knowing how something works often makes you more adept
at working with it, extending it, or fi xing it when it breaks. Just as a race car driver benefi ts from
a fundamental knowledge of combustion engines, aerodynamics, and the mechanics of automobile
suspension, someone driving WordPress through its full dynamic range will be signifi cantly more
adept once acquainted with the underlying software physics.