Defining good caching scenarios - php

Question

I need to know if I can improve the way I cache my api calls from the inside of my CodeIgniter app.The way I do it right now is like this, in a hmvc pattern:
Controller HOME == calls to => module app/application/modules/apis/controllers/c_$api == loads library => app/application/libraries/$api ==> Library returns response to module's controller_X, the controller invokes the view with the data it has
//Note: My app does not use twitter api, but others
Inside the apis module is where the all the apc caching is happening, like so:
// Load up drivers
$this->load->library('driver');
$this->load->driver('cache', array('adapter' => 'apc'));
// Get Tweets from Cache
$tweets = $this->cache->get('my_tweets');
if ( ! $tweets)
{
// No tweets in the cache, so get new ones.
$url = 'http://api.twitter.com/1/statuses/user_timeline.json?screen_name=gaker&count=5';
$tweets = json_decode(file_get_contents($url));
$this->cache->save('my_tweets',$tweets, 300);
}
return $tweets;
as explained in this article: http://www.gregaker.net/2011/feb/12/codeigniter-reactors-caching-drivers/
So I was wondering:
Having 3 scenarios: home, query, result; in each module apis's controller, do you think it would be a good idea to implement cache for each controller with all the scenarios? example:
//for each api1, api2 ... apiX, apply this:
//home
$this->cache->save('api_home',$api_home, 300);
//query
$this->cache->save("api_$query", $api_{$query}, 300); // I don't know for sure if $api_{$query} works or not, so don't hang me because I haven't tried it.
//result
$this->cache->save("api_$queryId", $api_{$queryId}, 300);
Even though I cached the api call, do you think I should cache the result in the controller that is calling the api module controller, with the same 3 scenarios (home, query and result)? Like so:
//modules/{home,fetch,article}/controllers/{home,fetch,article}.php
//home
$homeData['latest'][$api] = modules::run("apis/c_$api/data", array('action'=>'topRated'));
$this->cache->save('home_data', $home_data, 300);
//query
$searchResults[$api] = modules::run("apis/c_$api/data", $parameters);
$this->cache->save("search_results_$query", $search_results_{$query}, 300);
//article page
$result = modules::run("apis/c_$api/data", $parameters);
$this->cache->save("$api_article_$id", ${$api}_article_{$id}, 300);
So, what do you think? Is it a good practice the mentioned above, or just an awful stupid one?
//Note, the suggested caching ideas were not tested... so, I don't know if ${$api}_article_{$id} will work or not (even though I suppose it will)

Answer 1

IMHO It is a good idea to cache api results if you don't need real time data. If you don't care that you won't see new data for an hour, then by all means cache it for an hour. So for your first question, you just need to ask yourself: "How fresh does the content need to be for my application?" and implement caching accordingly.
For the second question: I don't see a lot of value in caching content if it's only been manipulated in simple ways. At that point you're using up space in your cache and not getting a lot of value. But if there are database, or other api calls being made using that data, then yes they should be cached using a technique similar to the above.
If you're that worried about processor load (the only reason to cache content after manipulation) you're best bet is to look at something like Varnish or CloudFront.