Smarty caching components

Question

The Smarty FAQ suggests one way to handle cacheable fragments, but it needs each page controller to do tons of work up-front, instead of encapsulating things properly.

We want to get to a stage where we can do something like:

<div id="header">
  {our_categories}
  {our_subcategories category=$current_category}
</div>

The output of the our_ prefixed functions should be completely cacheable, only relying on the named parameters (if any.) If we referred to {our_categories} in more than one template, they should all refer to the same cached content.

(it's probably worth mentioning that we tried using {insert name="..."} and coding up our own functions, but the results weren't cacheable, and we ended up hand-cranking the HTML retunred, rather than benefiting from Smarty's template processing.)

Our first crack at this uses a custom function smarty_function_our_categories, but the caching's going horribly wrong. Here's what our function looks like:

function smarty_function_our_categories($params, &$smarty) {
  $smarty->caching = 2;
  $smarty->cache_lifetime = 3600; # 1 hour
  if (!$smarty->is_cached(...)) {
    // ... do db access to fetch data for template...
    $smarty->assign(....);
  }
  return $smarty->fetch(...);
}

The problem is: calling $smarty->fetch() within a function confuses smarty, making it lose track of which templates have insert-tags, and which don't. The end result is that Smarty forgets to replace certain markers when serving up cached content (markers it puts there to say: "replace this with the results of some non-caching {insert ...} call.) In our case, this manifests itself with our site showing a couple of md5 checksums and a php-serialized memento where our main menu should be - that's not good.

We assume we've made a mistake in how we're building our components, so the question finally becomes:

How do you safely create a caching component using Smarty to render itself?

Answer 1

You should not change caching parameters from inside Smarty function. Wheither or not the result of the plugin output is cacheable is defined when you register plugin.

http://www.smarty.net/manual/en/caching.cacheable.php

To create uncachable content inside cachable template just use {dynamic} blocks like this:

//Registering dynamic non-caching block with Smarty
$template->register_block('dynamic', 'smarty_block_dynamic', false); 
function smarty_block_dynamic($param, $content, &$smarty) { 
    return $content; 
}