kmvan

finally i edit the source, all OK.
thinks.

plugin page means the my-plugin-name.php.
for example:
my-plugin-name.php:

<?php
/*
Plugin Name: my plugin
Plugin URI: ....
...
*/
if(is_user_logged_in()){
 function example(){
  ...
 }
}
?>

like this, it shows me a error: the is_user_logged_in() is undefined.
but like this:

<?php
/*
Plugin Name: my plugin
Plugin URI: ....
...
*/
function example(){
 if(is_user_logged_in()){
  ...
 }
}
?>

it works!
can get me?

now i write the is_user_logged_in() in the function,it works.but the outside.

this plugin has a widget already
http://wordpress.org/extend/plugins/top-comments/

it’s just thumbs up, have not thumbs down?