Widgets are typically stored in the app/Widgets directory. Once you're ready to register a widget with WordPress you can do so in app/widgets.php.
When defining a widget it must extend the WP_Widget class. Here is an example of a basic widget class:
app/Widgets/MyWidget.php
<?php namespace MyPlugin\Widgets;
class MyWidget extends \WP_Widget {
public function __construct() {
}
public function widget( $args, $instance ) {
// outputs the content of the widget
}
public function form( $instance ) {
// outputs the options form on admin
}
public function update( $new_instance, $old_instance ) {
// processes widget options to be saved
}
}Now, we can register this widget like so:
app/widgets.php
$widget->add(__NAMESPACE__ . '\Widgets\MyWidget');