It took me a while, but I figured out how to get this to work with MySQLi. It will also still work with MySQL, so it probably should be substituted into the plug-in for all users.
Find:
PHP Code:
AND pm.folderid=" . mysql_real_escape_string($_GET['folderid']) . " ";
or, if you've already made the change mentioned in Post #103:
PHP Code:
AND pm.folderid=" . mysql_real_escape_string($search_folderid) . " ";
And replace it with:
PHP Code:
AND pm.folderid=" . $db->escape_string($search_folderid) . " ";