Welcome to the introduction to developing WordPress plugins.

What is a plugin?

A WordPress plugin is a package of code that can be installed on a WordPress website to add new features or functionality.

Whereas themes are used to control the look and feel of a WordPress site, plugins are used to add to or extend its functionality.

Why use a plugin?

As a WordPress developer, you will often need to create custom functionality for a WordPress website.

While it is possible to add this functionality to a theme or child theme’s functions.php file, it often makes more sense to add this code to a WordPress plugin.

This is because a plugin can be activated or deactivated without affecting the theme.

Not only that but the same plugin can be used across multiple sites.

The WordPress plugin directory

The WordPress plugin directory contains over fifty thousand plugins that can be installed on a WordPress site.

These plugins can turn a WordPress site into an online store, a social network, a learning management system, and much more.

The structure of a WordPress plugin

Most WordPress plugins in the plugin directory are composed of many files, but to create a valid plugin you only really need one main PHP file with a specifically formatted comment block, also known as a DocBlock, at the top of that file.

When installed, plugins exist inside the wp-content/plugins directory of a WordPress site.

Hello Dolly, one of the first plugins for WordPress, is an example of a single file plugin. All the functionality of the plugin is contained in a single PHP file called hello.php.

Akismet, an anti-spam plugin for WordPress, is an example of a multi-file plugin. Here the akismet directory contains all the files for the plugin. The main file for the plugin is akismet.php and it handles the loading of all the other required files.

The plugin developer handbook

The WordPress plugin developer handbook is a great resource for learning how to create a WordPress plugin. It contains information on how to create a plugin, how to use the various WordPress APIs, and how to submit a plugin to the WordPress plugin directory.

You can find the plugin developer handbook by visiting developer.wordpress.org and clicking on the “Plugins” link at the top of the page.