The widgets_init action hook is used to register a function to be executed when widgets are being created by WordPress. When the callback occurs, we create a new widget by calling the simple register_widget function. As can be seen in the recipe, this function requires a single argument that indicates the name of the class that contains the widget definition.

The rest of the recipe declares the widget implementation class, which extends the WordPress WP_Widget class. While the class has many potential member methods, this recipe only defines the class constructor, which initializes the object instance by specifying a unique identifier, a title, and a description embedded within an array of optional parameters. As with any other functions declared in plugins, it is important to give unique names to the widget class and widget identifier in order to avoid conflict with other plugins.

When the plugin is activated, users can see the new widget immediately and are able to add one or more instances of the new element as part of a sidebar's content. However, the new widget will not render anything other than an error message on website pages until its widget method is implemented in a later recipe in this chapter.