smarty 截取字符串长度

$smarty = new Smarty;
$smarty->assign('articleTitle', 'Two Sisters Reunite after Eighteen Years at Checkout Counter.');
$smarty->display('index.tpl');

index.tpl:

{$articleTitle}
{$articleTitle|truncate}
{$articleTitle|truncate:30}
{$articleTitle|truncate:30:""}
{$articleTitle|truncate:30:"---"}
{$articleTitle|truncate:30:"":true}
{$articleTitle|truncate:30:"...":true}

OUTPUT:

Two Sisters Reunite after Eighteen Years at Checkout Counter.
Two Sisters Reunite after Eighteen Years at Checkout Counter.
Two Sisters Reunite after...
Two Sisters Reunite after
Two Sisters Reunite after---
Two Sisters Reunite after Eigh
Two Sisters Reunite after E...