How to create a WordPress plugin

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Use actions and filters to do things with your 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');

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Create a basic plugin

Use actions and filters to do things with your plugin

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