Building a Newsletter Subscription Plugin for WordPress

Posted on 21st June 2023

Building a Newsletter Subscription Plugin for WordPress

As a WordPress developer, you may be asked to build a plugin that allows visitors to subscribe to a newsletter. In this article, we’ll show you how to build a newsletter subscription plugin for WordPress.

We’ll assume that you’re familiar with the basics of plugin development. If not, we recommend reading our guide on how to create a WordPress plugin.

Step 1: Create a Plugin Folder and File

First, you’ll need to create a folder for your plugin. We’ll call our plugin “Newsletter Subscription”.

Next, create a file in this folder called “newsletter-subscription.php”. This will be the main plugin file.

Step 2: Add a Plugin Header

Every WordPress plugin must have a plugin header. This is a comment block at the top of the main plugin file. The header tells WordPress what the plugin is called, who wrote it, and other important information.

Here’s an example plugin header for our newsletter subscription plugin:

‘newsletter_subscription_widget’,
‘description’ => ‘A widget that allows visitors to subscribe to a newsletter.’,
);
parent::__construct( ‘newsletter_subscription_widget’, ‘Newsletter Subscription Widget’, $widget_ops );
}

/**
* Outputs the content of the widget
*
* @param array $args
* @param array $instance
*/
public function widget( $args, $instance ) {
// outputs the content of the widget
}

/**
* Outputs the options form on admin
*
* @param array $instance The widget options
*/
public function form( $instance ) {
// outputs the options form on admin
}

/**
* Processing widget options on save
*
* @param array $new_instance The new options
* @param array $old_instance The previous options
*
* @return array
*/
public function update( $new_instance, $old_instance ) {
// processes widget options to be saved
}
}

Step 4: Add a Shortcode

In addition to registering a widget, you may also want to add a shortcode. Shortcodes are small bits of code that can be used to insert content into posts and pages.

To add a shortcode, you’ll need to use the WordPress shortcodes API. First, you’ll need to register a shortcode using the add_shortcode() function. This function takes two arguments: the shortcode tag and a callback function.

The callback function is responsible for returning the content that will be inserted into the post or page. This content can be anything, from simple text to complex HTML.

Here’s an example shortcode for our newsletter subscription plugin:

function newsletter_subscription_shortcode() {
return ‘

Subscribe to our newsletter!

‘;
}
add_shortcode( ‘newsletter_subscription’, ‘newsletter_subscription_shortcode’ );

Step 5: Enqueue Styles and Scripts

If your plugin needs to load any CSS or JavaScript files, you’ll need to use the WordPress enqueueing system.

The wp_enqueue_style() function is used to load CSS files. This function takes two arguments: the handle of the stylesheet and the URL of the stylesheet.

The wp_enqueue_script() function is used to load JavaScript files. This function takes two arguments: the handle of the script and the URL of the script.

Here’s an example of how to enqueue a stylesheet and a JavaScript file:

function newsletter_subscription_enqueue_scripts() {
wp_enqueue_style( ‘newsletter-subscription-styles’, plugins_url( ‘newsletter-subscription.css’, __FILE__ ) );
wp_enqueue_script( ‘newsletter-subscription-scripts’, plugins_url( ‘newsletter-subscription.js’, __FILE__ ) );
}
add_action( ‘wp_enqueue_scripts’, ‘newsletter_subscription_enqueue_scripts’ );

Step 6: Register an Action Hook

If you want to insert content into the section of the website, you’ll need to use an action hook.

Action hooks allow you to insert content or run code at specific points in the WordPress code. There are two types of action hooks: WordPress core hooks and plugin hooks.

WordPress core hooks are defined by the WordPress developers and cannot be changed. Plugin hooks, on the other hand, are defined by plugin developers and can be changed.

In our newsletter subscription plugin, we’ll use the wp_head action hook. This hook is called by WordPress just before the tag.

To use an action hook, you’ll need to call the add_action() function. This function takes two arguments: the name of the hook and a callback function.

The callback function is responsible for returning the content that will be inserted into the post or page. This content can be anything, from simple text to complex HTML.

Here’s an example of how to use the wp_head action hook:

function newsletter_subscription_wp_head() {
echo ‘‘;
}
add_action( ‘wp_head’, ‘newsletter_subscription_wp_head’ );

Step 7: Register a Filter Hook

If you want to modify content that has already been inserted into the database, you’ll need to use a filter hook.

Filter hooks allow you to modify content or run code at specific points in the WordPress code. There are two types of filter hooks: WordPress core hooks and plugin hooks.

WordPress core hooks are defined by the WordPress developers and cannot be changed. Plugin hooks, on the other hand, are defined by plugin developers and can be changed.

In our newsletter subscription plugin, we’ll use the the_content filter hook. This hook is called by WordPress just before the content is displayed on the screen.

To use a filter hook, you’ll need to call the add_filter() function. This function takes two arguments: the name of the hook and a callback function.

The callback function is responsible for returning the modified content.

Here’s an example of how to use the the_content filter hook:

function newsletter_subscription_the_content( $content ) {
return $content . ‘

Subscribe to our newsletter!

‘;
}
add_filter( ‘the_content’, ‘newsletter_subscription_the_content’ );

Step 8: Create a Settings Page

If your plugin needs to store any settings, you’ll need to create a settings page. Settings pages are used to store plugin settings in the WordPress admin area.

To create a settings page, you’ll need to use the WordPress settings API. First, you’ll need to register a setting using the register_setting() function. This function takes three arguments: the name of the setting, the name of the group, and an array of arguments.

Next, you’ll need to add a settings field using the add_settings_field() function. This function takes five arguments: the name of the field, the title of the field, a callback function, the name of the page, and an array of arguments.

The callback function is responsible for outputting the field HTML.

Here’s an example of how to create a settings page:

function newsletter_subscription_register_settings() {
register_setting( ‘newsletter_subscription_settings’, ‘newsletter_subscription_setting_1’, ‘intval’ );
add_settings_field( ‘newsletter_subscription_setting_1’, ‘Setting 1’, ‘newsletter_subscription_setting_1_callback’, ‘newsletter_subscription_settings’, ‘newsletter_subscription_section_1’ );
}
add_action( ‘admin_init’, ‘newsletter_subscription_register_settings’ );

function newsletter_subscription_setting_1_