Widget sampte to test Checkbox field

functions.php

class MY_Widget extends WP_Widget {

    public function __construct() {
        parent::__construct( 'my_widget', 'My Widget', array(
            'classname'   => 'my-widget',
            'description' => 'Testing checkbox fields.',
        ) );
    }

    public function widget( $args, $instance ) {
        echo $args['before_widget'];
            echo '<pre>'; var_dump( $instance ); echo '</pre>';
        echo $args['after_widget'];
    }

    public function update( $new_instance, $old_instance ) {
        $instance = $old_instance;

        $instance['cb1'] = isset( $new_instance['cb1'] ) ? 'yes' : 'no';
        $instance['cb2'] = isset( $new_instance['cb2'] ) ? 'yes' : 'no';

        return $instance;
    }

    public function form( $instance ) {
        $instance = wp_parse_args(
            (array) $instance,
            // The default options.
            array(
                'cb1' => 'yes', // checked by default
                'cb2' => 'no',  // not checked by default
            )
        );
        ?>
            <p>
                <input type="checkbox" id="<?php echo $this->get_field_id( 'cb1' ); ?>" name="<?php echo $this->get_field_name( 'cb1' ); ?>" value="yes"<?php checked( 'yes', $instance['cb1'] ); ?>>
                <label for="<?php echo $this->get_field_id( 'cb1' ); ?>">Checkbox #1</label><br>

                <input type="checkbox" id="<?php echo $this->get_field_id( 'cb2' ); ?>" name="<?php echo $this->get_field_name( 'cb2' ); ?>" value="yes"<?php checked( 'yes', $instance['cb2'] ); ?>>
                <label for="<?php echo $this->get_field_id( 'cb2' ); ?>">Checkbox #2</label>
            </p>
        <?php
    }
}

/*-----------------------------------------------------------------------------------*/
/* REGISTRO IL WIDGET TEST */
/*-----------------------------------------------------------------------------------*/ 

if (!function_exists('test_load_post_widgets')) {

	function test_load_post_widgets() {
	
		register_widget( 'MY_Widget' );
	
	}
	
	add_action('widgets_init', 'test_load_post_widgets');

}