how to build WordPress plugin step-by-step with examples.

1. Choose a unique name and create a new directory with that name in the “wp-content/plugins” directory of your WordPress installation.
   • For example, if your plugin name is “Simple Lightbox,” create a directory named “simple-lightbox” in the plugins directory.
2. Create a new file with the same name as the directory, but with a “.php” extension, inside the directory you just created.
   • For example, “simple-lightbox.php”
3. Add plugin header information at the top of the file, including the plugin name, description, author, and version information

<?php
/*
Plugin Name: Simple Lightbox
Plugin URI: https://www.example.com/simple-lightbox
Description: A simple lightbox plugin for WordPress
Author: Your Name
Version: 1.0
*/

4. Write the plugin code using the WordPress API, hooks, and functions to achieve the desired functionality.
   • For example, to add a lightbox to all image links on a page, you could use the following code:

function simple_lightbox_add_lightbox($content) {
   $content = preg_replace('/<a(.*?)href=(?:\'|")(.*?).(bmp|gif|jpeg|jpg|png)(?:\'|")(.*?)>/i', '<a$1href=$2.$3$4 class="lightbox">', $content);
   return $content;
}
add_filter('the_content', 'simple_lightbox_add_lightbox');

5. Test the plugin by activating it in the WordPress admin panel.
6. If everything works, submit the plugin to the WordPress plugin repository for others to use.
7. Consider using best practices and security measures when writing your plugin code, such as using nonces for security, avoiding direct database queries, and proper sanitization and validation of user input.
   • For example, to add a nonce to a form in your plugin, you could use the following code:

$nonce = wp_create_nonce('simple_lightbox_form_nonce');
echo '<input type="hidden" name="simple_lightbox_form_nonce" value="' . $nonce . '">';

8. Make use of action and filter hooks to allow users to modify and extend the behavior of your plugin.
   • For example, to allow users to add custom styles for your lightbox, you could use the following code:

function simple_lightbox_add_styles() {
   wp_enqueue_style('simple-lightbox', plugins_url('simple-lightbox/lightbox.css'));
}
add_action('wp_enqueue_scripts', 'simple_lightbox_add_styles');

9. Use proper documentation and commenting within your code to make it easier for others to understand and use.
10. Regularly update and maintain your plugin, fixing bugs and adding new features as needed, to keep it functional and secure for users.

This should give you a better idea of how to build a simple WordPress plugin, with examples for each step. Good luck!