The Cache_Lite class comes courtesy of PEAR, the PHP Extension and Application Repository (http://pear.php.net). In case you didn't know, PEAR is an online repository of free PHP software, including classes and modules for everything from data archiving to XML parsing. When you install PHP, a whole bunch of PEAR modules get installed as well; the Cache_Lite class is one of them.

In case your PHP distribution didn't include Cache_Lite, you can get yourself a copy from the official PEAR Web site, at http://pear.php.net - simply unzip the distribution archive into your PEAR directory and you're ready to roll!

Let's begin with something simple - building a primitive cache using Cache_Lite object methods. Here's the code:

  <?php



// include the package



  require_once("Lite.php");


// set an ID for this cache



  $id = "starwars";


// set some variables



  $options = array(



  "cacheDir" => "cache/",



  "lifeTime" => 50



  );


// create a Cache_Lite object



  $objCache = new Cache_Lite($options);


// test if there exists a valid cache



  if ($quote = $objCache->get($id)) 



  {



  // if so, display it



  echo $quote;



  



  // add a message indicating this is cached output



  echo " [cached]";



  } 



  else 



  { 



  // no cached data



  // implies this data has not been requested in last cache lifetime



  // so obtain it and display it



  $quote = "Do, or do not. There is no try. -- Yoda, Star Wars"; 



  echo $quote; 



  



  // also save it in the cache for future use



  $objCache->save($quote, $id);



  }


?>



  

Don't worry if it didn't make too much sense - all will be explained shortly. For the moment, just feast your eyes on the output:

Do, or do not. There is no try. -- Yoda, Star Wars

Now refresh the page - you should see something like this, indicating that the second occurrence of the page has been retrieved from the cache.

Do, or do not. There is no try. -- Yoda, Star Wars [cached]

Let's take a closer look at how this was accomplished, on the next page.