A WordPress widget to display all attachments to a post/page of a certain type

cromwell-downloads-widget.php

<?php
/*
 * A WordPress widget that displays all PDF's attached to the current post
 * You can adapt this widget to extract other file types by altering the 'post_mime_type' => 'application/pdf'
 * argument refer to: http://en.wikipedia.org/wiki/Internet_media_type#List_of_common_media_types for mime types
*/

class Sennza_PDF_Download_Widget extends WP_Widget
{
    /** constructor */
    function __construct()
    {
        parent::WP_Widget( /* Base ID */
            'sennza_pdf_download_widget', /* Name */
            'Sennza PDF Download Widget', array( 'description' => 'A widget to display all pdf attachments for a page' ));
    }

    /** @see WP_Widget::widget */
    function widget( $args, $instance )
    {
        extract( $args );
        $title = apply_filters( 'widget_title', $instance['title'] );
        echo $before_widget;
        if ( !empty($title) ) {
            echo $before_title . $title . $after_title;
        }
        global $post;
        $args = array(
            'post_type' => 'attachment',
            'post_mime_type' => 'application/pdf',
            'numberposts' => -1,
            'post_status' => 'inherit',
            'post_parent' => $post->ID
        );
        $attachments = new WP_Query( $args );?>
    <aside id="attachments" class="widget">
        <ul class="downloads">
            <?php
            while ( $attachments->have_posts()) : $attachments->the_post(); ?>
                <li><a
                    href="<?php echo wp_get_attachment_url( $attachments->ID ); ?>"><?php echo $post->post_title; ?></a>
                    <span
                        class="download-details"><?php echo substr($post->post_mime_type, strpos($post->post_mime_type, '/') + 1) . ' - ' . size_format( filesize( get_attached_file($post->ID) ) ); ?></span>
                </li>
                <?php endwhile; ?>
        </ul>
    </aside>
    <?php echo $after_widget;
    }

    /** @see WP_Widget::update */
    function update( $new_instance, $old_instance )
    {
        $instance = $old_instance;
        $instance['title'] = strip_tags( $new_instance['title'] );
        return $instance;
    }

    /** @see WP_Widget::form */
    function form( $instance )
    {
        if ($instance) {
            $title = esc_attr( $instance['title'] );
        }
        else {
            $title = __( 'PDF Downloads', 'text_domain' );
        }
        ?>
    <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 $title; ?>"/>
    </p>
    <?php
    }

}

add_action( 'widgets_init', create_function( '', 'register_widget("sennza_pdf_download_widget");' ) );
?>