<?php
$smarty->caching = true;

function remaining_seconds($params, &$smarty) {
    $remain = $params['endtime'] - time();
    if($remain >= 0){
        return $remain . ' second(s)';
    }else{
        return 'done';
    }
}

$smarty->register_function('remaining', 'remaining_seconds', false, array('endtime'));

if (!$smarty->is_cached('index.tpl')) {
    // fetch $obj from db and assign...
    $smarty->assign_by_ref('obj', $obj);
}

$smarty->display('index.tpl');
?>

   

where index.tpl is:

Time Remaining: {remaining endtime=$obj->endtime}

   

The number of seconds till the endtime of $obj is reached changes on each display of the page, even if the page is cached. Since the endtime attribute is cached the object only has to be pulled from the database when page is written to the cache but not on subsequent requests of the page.

index.php:

<?php
$smarty->caching = 1;

function smarty_block_dynamic($param, $content, &$smarty) {
    return $content;
}
$smarty->register_block('dynamic', 'smarty_block_dynamic', false);

$smarty->display('index.tpl');
?>

   

where index.tpl is:

Page created: {'0'|date_format:'%D %H:%M:%S'}

{dynamic}

Now is: {'0'|date_format:'%D %H:%M:%S'}

... do other stuff ...

{/dynamic}