PHP & smarty - nested queries and arrays

Hello! I'm using PHP and Smarty to try to build an array of arrays using the results from nested queries. I am just learning about nested arrays, and I'm not sure what I'm doing wrong. I am hoping someone can give me a hint as to what I am doing wrong. I looked on php.net, but still couldn't figure it out. If I remove the PHP foreach loop, it works fine, except, of course, no sub projects show up. The error must be in there, but I'm just not seeing it. I get the following error with the code below:

    Warning: Smarty error: unable to read resource: "welcome/Object.tpl" in /usr/local/lib/php/Smarty/Smarty.class.php on line 1088
  PHP STUFF
$query ="SELECT * FROM projects WHERE parent_project_id is NULL OR parent_project_id = ''";

$projects = $db->getAssoc($query, DB_FETCHMODE_ASSOC); foreach ($projects as $key => $project) { $query ="SELECT * FROM projects WHERE parent_project_id = $projects[$key]['project_id']"; $sub = $db->getAssoc($query, DB_FETCHMODE_ASSOC); $projects[$key]['subs'] = $sub; } $tpl->assign('projects', $projects); SMARTY STUFF {foreach from=$projects item='entry'} <b>{$entry.short_name}</b><br /> <ul> {foreach from=$entry.subs item='sub'}

       <li>{$sub.short_name}</li>

{foreachelse}

       <li>No subs for this project</li>

{/foreach} </ul> {foreachelse} <b>No projects found</b> {/foreach} Can anyone point me in the right direction? Thanks, Amanda