[oroo]

I need to show the category list which stored in database on the sidebar. I tried to write php code in a seperate file and add this php file as a plugin. which is like follows:

php file: forum_leftbar_plugin.php

PHP Code:

<?php
    function display_categories() {
        $sql = "SELECT blablabla FROM blablabla";
        $result = mysql_query($sql);
        while($row = mysql_fetch_row($result)) {
            $categoryID = $row[0];
            $title = $row[1];
            print("
                <div class='leftsidebutton'>
                    <a href='#' class='link'>$title</a>
                </div>
            ");
        }
    }
    display_categories();
?>

and this is a plugin which I add into global_start of both Right Column and vBulletin product.

ob_start();
  include(path/to/file/forum_leftbar_plugin.php');
  $forum_leftbar_plugin = ob_get_contents();
ob_end_clean();

I actived either one of them at a time, but when I loaded page from ie browser, it gave me this error message: ('null' is null or not an object) And the left bar has been disappeared.

Please help me out here.