单击上载文件时，选择该文件，然后单击选择文件。我希望能够在单击更新之前或之后再次单击上载文件，并将所选文件添加到“my\\u file\\u URL”和“my\\u file\\u ID”元框中的现有值。但我在如何着手做这件事上遇到了一些困难。现在，它将删除以前的值。非常感谢您的帮助。非常感谢。代码如下：

功能。php

function add_resource($post){
$url = get_post_meta($post->ID, \'my_file_URL\', true);
$id = get_post_meta($post->ID, \'my_file_ID\', true);

?>

 <input id="my_file_URL" name="my_file_URL" type="text"
     value="<?php echo $url; ?>" style="width:400px;" />
 <input id="my_file_ID" name="my_file_ID" type="hidden"
     value="<?php echo $id; ?>" style="width:400px;" />
 <input id="my_upl_button" type="button" value="Upload File" /><br/>

 <script>
jQuery(document).ready(function($){

    var custom_uploader;

     $(\'#my_upl_button\').click(function(e) {

        e.preventDefault();

       //If the uploader object has already been created, reopen the dialog
        if (custom_uploader) {
            custom_uploader.open();
            return;
        } 

        //Extend the wp.media object
        custom_uploader = wp.media.frames.file_frame = wp.media({
            title: \'Choose File\',
            button: {
                text: \'Choose File\'
            },
            multiple: true
        });

        //When a file is selected, grab the URL and set it as the text field\'s value
        custom_uploader.on(\'select\', function() {
                var selection = custom_uploader.state().get(\'selection\').toJSON();

                var urls = selection.map( function(attachment){
                    return attachment.url;
                });
                var ids = selection.map( function(attachment){
                    return attachment.id;
                });

                for(i=0; i < selection.length; i++){

                        $( \'#my_file_URL\' ).after(
                            \'<br/><p>File URL: \' + selection[i].url + \'</p><p>  Description: \' + selection[i].description + \'</p><br/>\'
                        );
                }

                $( \'#my_file_URL\' ).val(urls.join(\',\'));
                $( \'#my_file_ID\' ).val(ids.join(\',\'));


            });


        //Open the uploader dialog
        custom_uploader.open();

    });

});

<?php
}

function save_meta_box($post_id){

    global $post;


            if(defined(\'DOING_AUTOSAVE\') && DOING_AUTOSAVE){
                return;
            } else {
                if (isset($_POST[\'my_file_URL\'])){

                    if(is_array($url))
                        $url[] = $new_url;
                    else
                        $url = array($new_url);

                    update_post_meta($post_id, \'my_file_URL\', $_POST[\'my_file_URL\']);

                }


                if (isset($_POST[\'my_file_ID\'])){

                    if(is_array($id))
                        $id[] = $new_id;
                    else
                        $id = array($new_id);

                    update_post_meta($post_id, \'my_file_ID\', $_POST[\'my_file_ID\']);

                }

            }


}
add_action(\'save_post\',\'save_meta_box\');

               $url = get_post_meta($post->ID, \'my_file_URL\', true);

               $id = get_post_meta($post->ID, \'my_file_ID\', true);

               $urls = explode(\',\', $url);

               $urlCount = count($urls);

               $ids = explode(\',\', $id);

              for($i=0; $i < $urlCount; $i++){ 

                 $fileID = $ids[$i];

                 $attachment_filesize = size_format( filesize( get_attached_file( $fileID ) ), 2 );

                 $date = get_the_date(\'M d, Y\', $fileID);

                 $attachment = get_post( $fileID ); ?>

                  <div class="codesc" style="float:left;"><h3><a href="<?php echo $urls[$i] ?>" target="_blank"><?php echo $attachment->post_title; ?><br>
                    <span class="linkdetails"><?php echo $attachment_filesize; ?> | <?php echo $date; ?></span></a></h3>
                    <p><?php echo $attachment->post_content; ?></p>
                  </div>

            <?php

              } ?>