Smarty ループフェッチが毎回同じ内容になるのはなぜですか?

<br />
foreach ( $category as $c ) {<br />
	$products = $util->getArrayByQueryString ( "select * from product_detail where sid=$c[id]" );<br />
	$smarty->assign ( "html_title", $c [name] . '：所有子类产品' );<br />
	$smarty->assign ( "products", $products );<br />
//	foreach ( $products as $p ) {<br />
//		echo $p [id] . $p [name] . '<br/>';<br />
//	}<br />
	$content = $smarty->fetch ( "products.tpl" );<br />
	$file_name = './products/' . $c [id] . '.html';<br />
	//html生成<br />
	create_html ( $file_name, $content );<br />
}<br />