count_sentences

index.php:

$smarty = new Smarty;
$smarty->assign('articleTitle', 'Two Soviet Ships Collide - One Dies. Enraged Cow Injures Farmer with Axe.');
$smarty->display('index.tpl');

index.tpl:

{$articleTitle}
{$articleTitle|count_sentences}

OUTPUT:

Two Soviet Ships Collide - One Dies. Enraged Cow Injures Farmer with Axe.
2