我用very rough 插件，用于向媒体文件添加有关艺术家的信息和URL。它需要一些调整（我需要时间），但它可以工作，并且可以演示如何添加额外字段以及如何在主题中使用它们：

<?php
/*
Plugin Name: Media Artist Field
Description: Adds two field to attachments – Artist and Artist URL – and adds this information to captions.
Version:     0.1
Author:      Fuxia Scholz
Created:     19.09.2010
*/
$Media_Artist = new Media_Artist(
    array (
        \'artist_name\' => array (
            \'public\' => \'artist_name\'
        ,   \'hidden\' => \'_artist_name\'
        ,   \'label\'  => \'Fotograf (Name)\'
        )
    ,   \'artist_url\' => array (
            \'public\' => \'artist_url\'
        ,   \'hidden\' => \'_artist_url\'
        ,   \'label\'  => \'Fotograf (URL)\'
        )
    )
,   \'Foto: \'
);
/**
 * Adds two fields for credits to any media file: name and URL.
 *
 * Based on the clear tutorial by Andy Blackwell:
 * @link http://net.tutsplus.com/?p=13076
 */
class Media_Artist
{
    public
        $fields = array (
            \'artist_name\' => array (
                \'public\' => \'artist_name\'
            ,   \'hidden\' => \'_artist_name\'
            ,   \'label\'  => \'Artist Name\'
            )
        ,   \'artist_url\' => array (
                \'public\' => \'artist_url\'
            ,   \'hidden\' => \'_artist_url\'
            ,   \'label\'  => \'Artist URL\'
            )
        )
        // Maybe its own field?
    ,   $caption_prefix
    ,   $br_before = TRUE;

    public function __construct(
        $fields         = array()
    ,   $caption_prefix = \'Source: \'
    ,   $br_before      = TRUE
    )
    {
        $this->fields         = array_merge($this->fields, $fields);
        $this->caption_prefix = $caption_prefix;
        $this->br_before      = (bool) $br_before;

        $this->set_filter();
    }

    public function set_filter()
    {
        add_filter(
            \'attachment_fields_to_edit\'
        ,   array ( $this, \'add_fields\' )
        ,   15
        ,   2
        );
        add_filter(
            \'attachment_fields_to_save\'
        ,   array ( $this, \'save_fields\' )
        ,   10
        ,   2
        );
        add_filter(
            \'img_caption_shortcode\'
        ,   array ( $this, \'caption_filter\' )
        ,   1
        ,   3
        );
    }

    public function add_fields($form_fields, $post)
    {
        foreach ( $this->fields as $field)
        {
            $form_fields[ $field[\'public\'] ][\'label\'] = $field[\'label\'];
            $form_fields[ $field[\'public\'] ][\'input\'] = \'text\';
            $form_fields[ $field[\'public\'] ][\'value\'] = get_post_meta(
                $post->ID
            ,   $field[\'hidden\']
            ,   TRUE
            );
        }
        return $form_fields;
    }

    public function save_fields($post, $attachment)
    {
        foreach ( $this->fields as $field)
        {
            if ( isset ( $attachment[ $field[\'public\'] ]) )
            {
                update_post_meta(
                    $post[\'ID\']
                ,   $field[\'hidden\']
                ,   $attachment[ $field[\'public\'] ]
                );
            }
        }

        return $post;
    }

    public function caption_filter($empty, $attr, $content = \'\')
    {
        /* Typical input:
         * [caption id="attachment_525" align="aligncenter"
         * width="300" caption="The caption."]
         * <a href="http://example.com/2008/images-test/albeo-screengrab/"
         * rel="attachment wp-att-525"><img
         * src="http://example.com/uploads/2010/08/albeo-screengrab4.jpg?w=300"
         * alt="" title="albeo-screengrab" width="300" height="276"
         * class="size-medium wp-image-525" /></a>[/caption]
         */
        extract(
            shortcode_atts(
                array (
                    \'id\'        => \'\'
                ,   \'align\'     => \'alignnone\'
                ,   \'width\'     => \'\'
                ,   \'caption\'   => \'\'
                ,   \'nocredits\' => \'0\'
                )
            ,   $attr
            )
        );

        // Let WP handle these cases.
        if ( empty ($id ) or 1 == $nocredits )
        {
            return \'\';
        }

        if ( 1 > (int) $width || empty ( $caption ) )
        {
            return $content;
        }

        if ( ! empty ( $id ) )
        {
            // Example: attachment_525
            $html_id     = \'id="\' . esc_attr($id) . \'" \';
            $tmp         = explode(\'_\', $id);
            $id          = end($tmp);

            $sub_caption = \'\';
            $artist_name = get_post_meta($id, $this->fields[\'artist_name\'][\'hidden\'], TRUE);
            $artist_url  = get_post_meta($id, $this->fields[\'artist_url\'][\'hidden\'], TRUE);

            // Okay, at least one value.
            if ( \'\' != $artist_name . $artist_url )
            {
                $sub_caption .= $this->br_before ? \'<br />\' : \'\';
                $sub_caption .= \'<span class="media-artist">\' . $this->caption_prefix;

                // No name given. We use the shortened URL.
                if ( \'\' == $artist_name )
                {
                    $sub_caption .= \'<a rel="author" href="\'
                        . $artist_url . \'">\'
                        . $this->short_url($artist_url)
                        . \'</a>\';
                } // We have just the name.
                elseif ( \'\' == $artist_url )
                {
                    $sub_caption .= $artist_name;
                } // We have both.
                else
                {
                    $sub_caption .= \'<a rel="author" href="\'
                        . $artist_url . \'">\'
                        . $artist_name
                        . \'</a>\';
                }

                $sub_caption .= \'</span>\';
            }

            $caption .= $sub_caption;
        }

        return \'<div \' . $html_id . \'class="wp-caption \' . esc_attr($align)
        . \'" style="width: \' . (10 + (int) $width) . \'px">\'
        . do_shortcode( $content ) . \'<p class="wp-caption-text">\'
        . $caption . \'</p></div>\';
    }

    public function short_url($url, $max_length=20)
    {
        $real_length = mb_strlen($url, \'UTF-8\');

        if ( $real_length <= $max_length )
        {
            return $url;
        }

        $keep = round( $max_length / 2 ) - 1;

        return mb_substr($url, 0, $keep, \'UTF-8\') . \'…\'
            . mb_substr($url, -$keep, $real_length, \'UTF-8\');
    }
    # @todo uninstall
}