http://codex.WordPress.org/Function_Reference/do_action

http://codex.WordPress.org/Function_Reference/add_action

代碼：

do_action('mytheme_aboveblog');

add_action('mytheme_aboveblog',  'mytheme_online_user_message');
 
function mytheme_online_user_message() { 
    global  $current_user; 
    if (!empty($current_user)) { 
        $user_login = addslashes($current_user->user_login); 
        echo "Hello {$user_login}!"; 
    } 
}