How to create a WordPress plugin

Create a basic plugin

At its simplest, a WordPress plugin is just a PHP file with a WordPress plugin header comment.

Here’s how to create a basic first plugin:

cd wp-content/plugins
mkdir hello-world && cd hello-world
vim hello-world.php

Write a basic plugin header comment:

<?php
/*
* Plugin Name:       My Basics Plugin
* Plugin URI:        https://example.com/plugins/the-basics/
* Description:       A simple WordPress plugin.
* Version:           0.0.1
* Requires PHP:      8.3.4
* Author:            John Smith
* Author URI:        https://author.example.com/
* License:           GPL v2 or later
*/

Now, your plugin should be listed on the plugins page:

Use actions and filters to do things with your plugin

You can use WordPress’s actions and filters to make your plugin do things.

• Actions let you add or change WordPress functionality.
• Filters let you alter content as it’s loaded or displayed on the website.

There are three basic hooks you’ll typically use when creating a plugin:

• register_activation_hook(): Lets you run code when your plugin is activated by the WP admin user (e.g., add custom database tables or set default option values).
• register_deactivation_hook(): Lets you run code when your plugin is deactivated (e.g., remove temporal data like cache or temporary files).
• register_uninstall_hook() : Lets you run code when your plugin is uninstalled (e.g., remove records from the options table.

Here’s an example plugin that does various things on being activated, deactivated, and uninstalled:

<?php
/*
* Plugin Name:       Hello World
* Plugin URI:        https://example.com/plugins/the-basics/
* Description:       A simple WordPress plugin.
* Version:           0.0.1
* Requires PHP:      8.3.4
* Author:            John Smith
* Author URI:        https://author.example.com/
* License:           GPL v2 or later
*/

// This function is called when the plugin is activated.
// Note: Using a prefix like `sthw` that identifies your plugin 
// (e.g., 'Sajad Torkamani Hello Word') for functions/classes is 
// considered a best practice for WordPress plugins to avoid 
// conflicts with other plugins.
function sthw_activate(): void
{
  sthw_create_file('hello_word_activated');
}

// This function is called when the plugin is deactivated.
function sthw_deactivate(): void
{
  sthw_create_file('hello_word_deactivated');
}

// This function is called when the plugin is uninstalled.
function sthw_uninstalled(): void
{
  sthw_create_file('hello_word_uninstalled');
}

function sthw_timestamp(): string
{
  return date('d-m-Y_h-i-s');
}

function sthw_create_file(string $filename): void
{
  $dir = ABSPATH . 'tmp/hello-world';
  
  if (!is_dir($dir)) {
    mkdir($dir, 0755, true);
  }
  
  touch("$dir/" . $filename . '_' . sthw_timestamp() . '.txt');
}

register_activation_hook(__FILE__, 'sthw_activate');
register_deactivation_hook(__FILE__, 'sthw_deactivate');
register_uninstall_hook(__FILE__, 'sthw_uninstall');

Links

• Plugin Basics – WordPress docs
• Best Practices
• Activation / Deactivation hooks
• Plugin API
• Options API