Create a Custom WordPress Widget

What is a WordPress Widget?

WordPress widgets were originally created to provide a simple and easy-to-use way of giving design and structure control of the WordPress theme to the user. The great thing about widgets is that you can drag and drop them into your sidebars or any widget ready areas of your website. This allows great flexibility to plugin and theme developers. They can add functionality into their products and let users decide when and where to use that functionality without messing with code. Similarly, as a user you can also create your own widgets in a site-specific plugin, so that you can drag and drop them into any theme you are using.

Creating a Widget in WordPress

Before we get started, it would be best if you create a site-specific plugin where you will be pasting widget code. You can also paste it in your theme’s functions.php file but a site-specific plugin is better.
In this tutorial, we will create a simple widget that just greets visitors. Take a look at this code and then paste it in your site-specific plugin to see it in action.

// Creating the widget 
class wpb_widget extends WP_Widget {

function __construct() {
parent::__construct(
// Base ID of your widget
'wpb_widget', 

// Widget name will appear in UI
__('WPBeginner Widget', 'wpb_widget_domain'), 

// Widget description
array( 'description' => __( 'Sample widget based on WPBeginner Tutorial', 'wpb_widget_domain' ), ) 
);
}

// Creating widget front-end
// This is where the action happens
public function widget( $args, $instance ) {
$title = apply_filters( 'widget_title', $instance['title'] );
// before and after widget arguments are defined by themes
echo $args['before_widget'];
if ( ! empty( $title ) )
echo $args['before_title'] . $title . $args['after_title'];

// This is where you run the code and display the output
echo __( 'Hello, World!', 'wpb_widget_domain' );
echo $args['after_widget'];
}
  
// Widget Backend 
public function form( $instance ) {
if ( isset( $instance[ 'title' ] ) ) {
$title = $instance[ 'title' ];
}
else {
$title = __( 'New title', 'wpb_widget_domain' );
}
// Widget admin form
?>
<p>
<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label> 
<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>" />
</p>
<?php 
}
 
// Updating widget replacing old instances with new
public function update( $new_instance, $old_instance ) {
$instance = array();
$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';
return $instance;
}
} // Class wpb_widget ends here

// Register and load the widget
function wpb_load_widget() {
 register_widget( 'wpb_widget' );
} 

add_action( 'widgets_init', 'wpb_load_widget' );




Now go to Appearance » Widgets, drag and drop WPBeginner Widget in your sidebar to see this custom widget in action.
Simple wasn’t it? First we created a custom widget. Then we defined what that widget does and how to display the widget back-end. Then we defined how to handle changes made to widget. Lastly, we registered and loaded the widget.
Now there are a few things that you might want to ask. For example, what wpb_text_domain does? WordPress uses gettext to handle translation and localization. This wpb_text_domain and __e tells gettext to make a string available for translation.