Tag: plugin-dev

WP: Delete Plugin Data On Uninstall

In the previous post, I created a plugin which stores some data in the database. Now I will add some code to it which will help to delete this data when the plugin is deleted or uninstalled via the plugins page.

When a plugin is deleted, the uninstall hook is called. I’m going to register the uninstall hook and ask it to call a function which removes our plugin data for us. Here’s the code for it:

register_uninstall_hook( __FILE__, 'my_fn_uninstall' );
function my_fn_uninstall() {
    delete_option( 'g_first_option' );
    delete_option( 'g_second_option' );
}

I’ve added this to the noice-plugin.php file I created in the previous post. If I try to delete the plugin now, it will display this message to me:

Once I hit OK, it will delete g_first_option and g_second_option from the wp_options table in the database.

WP: Add A Form To The Plugin Admin Page

In the previous post, I created a plugin page. And now I’ve added a form to it with the help of the following code:

<?php 
/*
Plugin Name: Noice Plugin
Plugin URI: https://csmumbai.com
Description: This plugin is Noice!
Author: Omkar Bhagat
Version: 1.0
*/ 
 
add_action('admin_menu', 'noice_create_menu');
 
function noice_create_menu() {
	add_options_page('Noice Plugin Title', 'Noice Plugin Settings', 'administrator', __FILE__, 'noice_settings_page');
}
 
function noice_settings_page() {
    echo '<h2>Hello Noice Person!</h2>';
?>
 
<form method="post" action="options.php">
 
    <table class="form-table">
 
        <tr>
        <th>First Field: </th>
        <td><input type="text" name="g_first_option" value="<?php echo get_option('g_first_option'); ?>" /></td>
        </tr>
 
        <tr>
        <th>Second Field: </th>
        <td><input type="text" name="g_second_option" value="<?php echo get_option('g_second_option'); ?>" /></td>
        </tr>
 
    </table>
        
    <p class="submit">
        <input type="submit" class="button-primary" value="<?php _e('Save Changes') ?>" />
    </p>
 
</form>
 
<?php } ?>

The lines which have been changed or added are highlighted in the code above. This gets us a form as follows:

At this point it does nothing because I’m yet to register these fields. In other words, WordPress doesn’t know what to do with these fields when the form is submitted.

<?php 
/*
Plugin Name: Noice Plugin
Plugin URI: https://csmumbai.com
Description: This plugin is Noice!
Author: Omkar Bhagat
Version: 1.0
*/ 
 
add_action('admin_menu', 'noice_create_menu');
 
function noice_create_menu() {
    add_options_page('Noice Plugin Title', 'Noice Plugin Settings', 'administrator', __FILE__, 'noice_settings_page');
    add_action( 'admin_init', 'noice_form_settings' );
}
 
function noice_form_settings() {
    register_setting('noice_form_settings_group', 'g_first_option');
    register_setting('noice_form_settings_group', 'g_second_option');
}
 
function noice_settings_page() {
    echo '<h2>Hello Noice Person!</h2>';
?>
 
<form method="post" action="options.php">
 
    <?php settings_fields('noice_form_settings_group'); ?>
 
    <table class="form-table">
 
        <tr>
        <th>First Field: </th>
        <td><input type="text" name="g_first_option" value="<?php echo get_option('g_first_option'); ?>" /></td>
        </tr>
 
        <tr>
        <th>Second Field: </th>
        <td><input type="text" name="g_second_option" value="<?php echo get_option('g_second_option'); ?>" /></td>
        </tr>
 
    </table>
        
    <p class="submit">
        <input type="submit" class="button-primary" value="<?php _e('Save Changes') ?>" />
    </p>
 
</form>
 
<?php } ?>

Here’s a short explanation of this code:

  1. Line 14: Added a way to call noice_form_settings function as admin_init is the action hook which is triggered before any other hook when a user accesses the admin area.
  2. Line 17-20: Registering the form fields with WP
  3. Line 28: This puts some hidden fields in the form to check if the request is valid. More on this here and here.

Entering something in the form and saving it returns this page:

The options will stay there even if I deactivate and reactivate the plugin. That’s fine but I’ll need to remove the data when the plugin is deleted/uninstalled. I’ll work on that in a future post.

Note: I can find this data in the database by going to wp_options table.

WP: Create A Plugin Admin Page

To create a WordPress plugin admin page, I’ll need to first add a menu item in the WP-Admin dashboard.

Instead of creating a totally new item using add_menu_page, I’m going to add my menu item under Settings option with the help of add_options_page function as follows:

<?php 
/*
Plugin Name: Noice Plugin
Plugin URI: https://csmumbai.com
Description: This plugin is NOICE!
Author: Omkar Bhagat
Version: 1.0
*/ 
 
 
// ONE
add_action('admin_menu', 'noice_create_menu');
 
// TWO
function noice_create_menu() {
	add_options_page('Noice Plugin Title', 'Noice Plugin Settings', 'administrator', __FILE__, 'noice_settings_page');
}
 
// THREE
function noice_settings_page() {
    echo '<p>Hello, this is a Noice Plugin!</p>';
}
 
?>

Here’s what I basically did:

  1. Added an action hook for admin_menu to call noice_create_menu
  2. noice_create_menu creates an options page for us with the following arguments:
    1. Page Title
    2. Menu Item Name
    3. Who can access it?
    4. Slug name (I used the file name here).
    5. Function to call to output content on the page
  3. noice_settings_page outputs content on the page

This results in the following menu item under the Settings option in WP-Admin dashboard –

And clicking on this new menu items takes me to –

Notice three things here:

  1. Output content – Hello, this is a Noice Plugin!
  2. Page title in the tab – Noice Plugin Title
  3. And the slug at the end of the URL – noice-plugin.php

This results in a simple WordPress admin page that prints some text. Let’s see how to do more with this in the next post.

WP: Hello World Plugin

In this post, let’s look at how to create a simple “Hello World” plugin in WordPress. By “Hello World” I mean a “basic” plugin that does nothing special but you can upload and install it on your WordPress site.

Creating The Plugin

The first step is to create a plugin folder and plugin file with the plugin name. Let’s name our plugin hello-world-replace.

This means our folder structure would look like this: hello-world-replace > hello-world-replace.php.

Enter the following code in the main plugin file hello-world-replace.php –

<?php 
/*
Plugin Name: Hello World
Plugin URI: https://csmumbai.com
Description: This plugin replaces all instances of "hello" with "Hello World"
Author: Omkar Bhagat
Version: 1.0
*/
 
function hello_world_replace( $text ) {
	return str_replace( 'hello', 'Hello World', $text );
}
 
add_filter('the_content', 'hello_world_replace');
 
?>

Save the file. Zip the folder. And the plugin is ready!

Testing The Plugin

To test the plugin, go to your site’s WP-Admin dashboard > Plugins > Add New and upload this zipped file.

Next create a post with hello text inside of it and publish it. Check the published version and you’ll find hello will be turned into Hello World.

That’s all in this post! 🙂