Creating a Plugin – The Basics

To create a WordPress plugin, you’ll need to create a plugin folder within the wp-content/plugins directory, then create a main PHP file with a header and write your plugin code, following WordPress’s plugin development guidelines. 

Here’s a more detailed breakdown:

Prerequisites:

Notice that these are things we included in this course beforehand to make sure you were ready to do the more complicated pieces.

• Basic PHP Knowledge: WordPress plugins are written in PHP, so you’ll need a foundational understanding of the language. 
• Access to Your WordPress Site: You’ll need access to your WordPress site’s file system (e.g., via FTP or a file manager). 

Create the Plugin Folder:

This is easier if you have direct access to the WordPress install folder. However, you can create your plugin locally, and then upload it to the server if you are working with a server which does not give direct access. When I am working on a remote server, this is what I do.

• Navigate to the wp-content/plugins directory on your WordPress installation. 
• Create a new folder with a descriptive name for your plugin (e.g., my-plugin). 

Create the Main Plugin File:

The next step will be to create a file. You may need multiple files for larger and more complex plugins. However, for your first, you probably only need one.

• Inside the plugin folder, create a PHP file named after your plugin, but with the .php extension (e.g., my-plugin.php). 
• Plugin Header: Add a plugin header comment block to the top of the file, including essential information like:
  • Plugin Name
  • Plugin URI
  • Description
  • Version
  • Author
  • Author URI
  • License
  • Text Domain. 

The code for your header would look like:

    <?php
    /*
    Plugin Name: My Plugin
    Plugin URI: https://example.com/my-plugin
    Description: A simple WordPress plugin
    Version: 1.0.0
    Author: Your Name
    Author URI: https://example.com
    License: GPL2
    Text Domain: my-plugin
    */
    ?>

Write Your Plugin Code:

After your PHP header, you’ll write your actually code like you would any other PHP file.

• Add your plugin’s code within the main PHP file. 
• Use WordPress’s API functions to interact with the core functionality, change or extend WordPress’s functionality. 
• Examples of plugin functionality:
  • Adding custom settings pages. 
  • Creating custom post types. 
  • Adding shortcodes. 
  • Hooking into WordPress actions and filters. 

Hooks

Hooks are how you decide when and where your plugin will execute it’s code. To make it more powerful for you the developer, WordPress has lots of places for you to put your hooks. Now actions and filters are a little different, but both work on the idea of them needing a function to call (not inline code).

Here is a (nearly) complete list of hooks that you can use to define when and where you place your plugin code: https://adambrown.info/p/wp_hooks/hook

Actions

“Actions allow you to add data or change how WordPress operates. Actions will run at a specific point in the execution of WordPress Core, plugins, and themes.” These operate as a callback function, and do not return any values.

Filters

“Filters give you the ability to change data during the execution of WordPress Core, plugins, and themes. Callback functions for Filters will accept a variable, modify it, and return it.”

Testing and Debugging: 

Always test and debug your code. Try to break it… see what happens, and what needs to be fixed.

• Activate your plugin in the WordPress dashboard (Plugins > Installed Plugins).
• Test your plugin thoroughly to ensure it functions as expected.
• Use WordPress’s built-in debugging tools to identify and fix any issues. 

Organizing Your Plugin Files (Optional): 

• For larger plugins, you might want to create additional folders and files to keep your code organized. 

I always have each plugin in its own folder. This just makes good organizational sense.

Readme File (Optional):

This is completely optional, and only if you plan on uploading to the WordPress repository, as they require it.

• Create a readme.txt file in your plugin folder, following the WordPress plugin guidelines for submitting to the WordPress repository. 

Compressing Your Plugin:

If I’m going to put it on a public server, I generally just add the plugin as I would any other plugin. That means making it into a zip file.

Note: It must be a zip file. You cannot use 7z, rar, or any other compression. It must be zip.

• Before submitting or distributing your plugin, compress the entire plugin folder into a ZIP file. 

Submitting to the WordPress Repository

If you want to submit your plugin to the WordPress repository, follow the guidelines provided by WordPress Developer Resources. You’ve already done some of these steps, most likely, such as creating the readme file. Read through their rules and make sure you are ready to go.

External Link: Introduction to Plugin Development

Creating a Plugin – The Basics was originally found on Access 2 Learn