Caching page by parts; how to pass variables calculated in cached parts into never-cached parts?

Question

Hello,

Let's imagine that I have a code like this...

if (!$data = $cache->load("part1_cache_id")) {
  $item_id = $model->getItemId();
  ob_start();
  echo 'Here is the cached item id: '.$item_id;
  $data = ob_get_contents();
  ob_end_clean();
  $cache->save($data, "part1_cache_id");
}
echo $data;

echo never_cache_function($item_id);

if (!$data_2 = $cache->load("part2_cache_id")) {
  ob_start();
  echo 'Here is the another cached part of the page...';
  $data_2 = ob_get_contents();
  ob_end_clean();
  $cache->save("part2_cache_id");
}
echo $data_2;

As far as you can see I need to pass $item_id variable into never_cache_function, but if fist part is cached (part1_cache_id) then I have no way to get $item_id value. I see the only solution - serialize all data from fist part (including $item_id value); then cache serialized string and unserialize it everytime when script is executed...

Something like this...

if (!$data = $cache->load("part1_cache_id")) {
  $item_id = $model->getItemId();
  $data['item_id'] = $item_id;
  ob_start();
  echo 'Here is the cached item id: '.$item_id;
  $data['html'] = ob_get_contents();
  ob_end_clean();
  $cache->save( serialize($data), "part1_cache_id" );      
}
$data = unserialize($data);
echo $data['html']

echo never_cache_function($data['item_id']);

Is there any other ways for doing such trick? I'm looking for the most high performance solution.

Thank you

UPDATED And another question is - how to implement such caching into controller without separating page into two templates? Is it possible?

PS: Please, do not suggest Smarty, I'm really interested in implementing custom caching.

Answer 1

You need to change your caching function to return an object or array. It would always have a data field that would contain the data and whatever other fields you need ie item_id.

Array(
  data => '<h1>whatever data you were caching before</h1>'
  item_id => 32,
  cache_date => '2010-03-01 12:32:01'
)

This will serialize/deserialze just fine and you would have access to additional parameters attached to your cached data.

Does this make sense?