现在可以完美运行。更新了代码。谢谢新家具。
  function foo_options(){
           global $post;
   if (isset($custom['website_url']) && isset($custom['website_url'][0])) {
   $website_url = isset($custom['website_url']) ? $custom['website_url'][0] : '';}
   ?>
<div id="foo-options">
<label>Website URL:</label><input name="website_url" value="<?php echo $website_url; ?>" />     
</div><!--end foo-options--> 
<?php
   }
{
   function update_website_url(){
       global $post;   
       if (($post != null) && isset($_POST['website_url'])) {
       update_post_meta($post->ID, "website_url", $_POST["website_url"]);
     }
  }
更新了代码和 bin。http://pastebin.com/2ZWisprm