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window because the HTML will be riddled with additional tag and style information. Finally, a variety of standalone editors publish to WordPress using the Atom Publishing Protocol or XML-RPC. Options for enabling posts to be published remotely are, as you would expect, in the Dashboard’s Settings section under Writing options.

      Click Publish for your own “Hello World” moment. Multiple subsystems created that editing pane, saved the content in a database, generated and saved the referential metadata, and then emitted nice-looking HTML. Most of the user-visible pieces are governed through the Dashboard and certain functions will be covered in various chapters.

      SUMMARY

      This chapter covered how WordPress got to where it is today with a brief history lesson and also touched on its current popularity. Part of WordPress’s rise in the web realm is attributed to the simplicity of the installation process. The next chapter dives into the core of WordPress so that you can take advantage of its extensibility, friendly design, and function.

      2

      Code Overview

      WHAT’S IN THIS CHAPTER?

      ● Downloading WordPress

      ● Configuring wp-config.php and .htaccess

      ● Exploring the wp-content directories

      ● Enabling maintenance mode in WordPress

      WordPress is a software package that comprises groups of source code files that perform specific tasks within the system. Understanding the code, including file and folder structure, is essential to understanding how WordPress works as a whole.

      After reading this chapter, you will be familiar with downloading and exploring the WordPress filesystem. This chapter also discusses configuring key WordPress files, including the powerful wp-config.php and .htaccess files. It also covers some advanced configuration options available in WordPress.

      DOWNLOADING

      The first step to installing WordPress is to download the source files required for WordPress to run. This section digs deeper into the core of WordPress.

Download Locations

      You can download the latest stable release of WordPress directly from WordPress.org by visiting the download page located at http://wordpress.org/download/.

      You can also update WordPress directly from your current WordPress installation by visiting the Updates WordPress section under the Dashboard ➢ Updates screen. Click the Download button to download the latest version of WordPress to your computer.

      WordPress also features Subversion (SVN) access. Subversion is a free, open source version control system. WordPress uses Subversion to manage files and directories and the changes made to them. You can download the latest WordPress source code by checking out http://core.svn.wordpress.org/trunk/.

      The SVN trunk directory contains the bleeding edge version of WordPress that is actively being developed. Typically, this version of WordPress contains bugs and is generally used for testing purposes. Running a production website using the trunk version of WordPress is not recommended.

      SVN is the mechanism developers use to actively develop on the WordPress core software. With SVN, you can create and submit patch files for inclusion into the WordPress core. Chapter 16 covers this in detail.

      Git is another very popular source code management system. Many developers, and not just in the WordPress community, have switched from SVN to Git for version control because of the many benefits Git offers over SVN. The WordPress core team has set up a Git mirror for WordPress core development. To access the Git repository run the command git clone git://develop.git.wordpress.org/. For more information on working with Git and WordPress core development, visit http://make.wordpress.org/core/2014/01/15/git-mirrors-for-wordpress/.

      The SVN and Git repositories are considered equals, so if you plan to work with the WordPress core you can use the version control system that you are most comfortable with.

Available Formats

      The default format for the WordPress software download is in a compressed zip archive named latest.zip. You can also download WordPress in a compressed tar archive named latest.tar.gz. There is no difference between the files in the archive, only the compression method used.

      You can download the zip and tar archives directly from these URLs:

      ● http://wordpress.org/latest.zip

      ● http://wordpress.org/latest.tar.gz

      These download links never change. Each new version of WordPress is automatically compressed and saved at this location when the version is tagged. When you save the archive to your computer, you should rename the file to include the WordPress version number, such as wordpress-4.1.zip. This will help you remember what version of WordPress you saved to your computer.

Release Archive

      WordPress.org features a release archive for WordPress. The Release Archive features a list of downloadable archives for every release of WordPress since version 0.71. The archive is located at http://wordpress.org/download/release-archive/.

      Remember that only the most current version of WordPress is actively maintained so these downloads are more for reference than actual use. “Actively maintained” means that critical fixes for security, performance, or reliability problems are made to the active branch and not applied retroactively to previous releases. If you need the fix, you’ll need to upgrade your installed version of WordPress.

      Another great use for these older versions of WordPress is to roll a website back to a previous version. For example, if you update a very old version of WordPress to the latest stable version and run into problems, you could easily download the old version that the website was originally running to revert to. The Release Archive also features a download for every beta and release candidate version of WordPress as well. This is great to see the overall growth of WordPress as a software platform.

      The release archives are also useful if you need to update an old version of WordPress that has hacks made to the core. Simply compare the website’s WordPress source code with the same version of WordPress from the release archive and any differences, or core hacks, will be discovered.

      DIRECTORY AND FILE STRUCTURE

      The WordPress source code features many different PHP, JavaScript, and CSS code files. Each file serves a specific purpose in WordPress. The beauty of open source software is that all code is publicly available, which means you can easily explore the code to better understand how WordPress functions. The best resource for learning WordPress is the WordPress software itself.

After extracting the WordPress download, you will notice the set file structure for WordPress, as shown in Figure 2.1.

Figure 2.1 Default WordPress file and folder structure

      WordPress comes with three directories by default: wp-admin, wp-content, and wp-includes. Core files are all files in the wp-admin and wp-includes directories and the majority of the files in the root WordPress directory. The wp-content directory holds all of your custom files, including themes, plugins, and media. This directory contains the code that controls content manipulation and presentation in WordPress. WordPress HTML content, such as pages and posts, is stored in the MySQL database along with metadata such as tag and category structures, both of which are covered in detail in Chapter 6.

      Modifying any of the core WordPress files can result in an unstable website. An innocuous but badly executed change to the Dashboard or login functions,

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