WordPress: Sidebar Comment Form Widget

<?php
/**
 * wpmidia custom Widgets - Sidebar Comment Form Widget
 *
 * @package WordPress
 * @subpackage wpmidia
 * @author Miriam de Paula - http://wpmidia.com.br
 * @since 22/06/2012 - v1
 */
class sidebar_commentform_Widget extends WP_Widget
{

        function sidebar_commentform_Widget(){
            $widget_ops = array( 'description' => 'Exibe o formulário de comentários na sidebar' );
            $control_ops = array( 'width' => 250, 'height' => 200 );
            parent::WP_Widget( false, $name = 'Sidebar Comment Form', $widget_ops, $control_ops );
        }

        /* Displays the Widget in the front-end */
        function widget( $args, $instance ){

            if(is_single()) {

                extract($args);

                global $post;
                $title = apply_filters( 'widget_title', empty( $instance['title'] ) ? 'Comentários' : esc_html( $instance['title'] ) );

                echo $before_widget;

                if ( ! empty( $title ) )
                    echo $before_title . $title . $after_title;

                comments_template( '', true );

                echo $after_widget;

            }
        }

        /*Saves the settings. */
        function update( $new_instance, $old_instance ){
            $instance = $old_instance;
            $instance['title'] = strip_tags( $new_instance['title'] );

            return $instance;
        }

        /*Creates the form for the widget in the back-end. */
        function form( $instance ){
            //Defaults
            $instance = wp_parse_args( (array) $instance, array( 'title' => 'Comentários', 'qtd_agenda' => 5 ) );

            $title = esc_attr( $instance['title'] );

            # Title
            echo '<p><label for="' . $this->get_field_id('title') . '">' . 'Título:' . '</label><input class="widefat" id="' . $this->get_field_id('title') . '" name="' . $this->get_field_name('title') . '" type="text" value="' . $title . '" /></p>';


        }

}

function sidebar_commentform_Widget_Init() {
    register_widget('sidebar_commentform_Widget');
}

add_action('widgets_init', 'sidebar_commentform_Widget_Init');
?>