PHP Category Iteration

$catrefs = array();
$catlist = array();
foreach($categories as $tmp) {

    $thisref = &$catrefs[ $tmp['id'] ];
    $thisref['parent_id'] = $tmp['parent'];
    $thisref['name'] = $tmp['name'];
    $thisref['products'] = $tmp['products'];
    $thisref['totals'] = $tmp['products'];

    if($tmp['parent'] == 0) {

        $catlist[ $tmp['id'] ] = & $thisref;
    }
    else {

        $catrefs[ $tmp['parent'] ]['children'][ $tmp['id'] ] = &$thisref;
    }
}