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• Created: 28 Sep 11

  Caching Class

   

  Intro

   
  Actually, I have taken the implementation from here, modified it a little bit:
  • Added default TTL to a month
  • Made a singleton class
  • Created a method which returns / checks if the cache directory exists

   

  The code

  class FileCache {

   

      static private $instance = NULL;

   

      private function __construct() {

          

      }

   

      static private function get_instance() {

          if (is_null(self::$instance)) {

              self::$instance = new FileCache();

          }

          return self::$instance;

      }

   

      // This is the function you store information with

      static public function store($key, $data, $ttl = null) {

   

          // set the default TTL to a month

          if (is_null($ttl)) {

              $ttl = 30 * 24 * 60 * 60;

          }

   

          $_this = self::get_instance();

   

          // Opening the file

          $h = fopen($_this->getFileName($key), 'w');

          if (!$h) {

              throw new Exception('Could not write to cache');

          }

          

          // Serializing along with the TTL

          $data = serialize(array(time() + $ttl, $data));

          if (fwrite($h, $data) === false) {

              throw new Exception('Could not write to cache');

          }

          fclose($h);

      }

   

      static public function clear($key) {

          $_this = self::get_instance();

          $filename = $_this->getFileName($key);

          if (file_exists($filename)) {

              @unlink($filename);

          }

      }

   

      private $cache_dir_name = NULL;

   

      private function _check_directory_exists() {

          if (is_null($this->cache_dir_name)) {

              $this->cache_dir_name = dirname(__FILE__) . '/_cache';

          }

          if (!is_dir($this->cache_dir_name)) {

              mkdir($this->cache_dir_name, true);

          }

      }

   

      // General function to find the filename for a certain key

      private function getFileName($key) {

          $_this = self::get_instance();

          $_this->_check_directory_exists();

          return $_this->cache_dir_name . '/s_cache' . md5($key);

      }

   

      // The function to fetch data returns false on failure

      static public function fetch($key) {

          $_this = self::get_instance();

          $filename = $_this->getFileName($key);

          if (!file_exists($filename) || !is_readable($filename))

              return false;

   

          $data = file_get_contents($filename);

   

          $data = @unserialize($data);

          if (!$data) {

   

              // Unlinking the file when unserializing failed

              unlink($filename);

              return false;

          }

   

          // checking if the data was expired

          if (time() > $data[0]) {

   

              // Unlinking

              unlink($filename);

              return false;

          }

          return $data[1];

      }

   

  }

   

  Summary

   
  It's simple, useful and lightweight. You can feel free to use it.
   
  Enjoy,
  Gregory C.