php缓存类

<?phpfinal class Cache { private $expire = 3600;   public function __construct() {$files = glob(DIR_CACHE . 'cache.*');if ($files) {foreach ($files as $file) {$time = substr(strrchr($file, '.'), 1);      if ($time < time()) {if (file_exists($file)) {@touch($file);@unlink($file);}      }    }}  }public function get($key) {$files = glob(DIR_CACHE . 'cache.' . $key . '.*');if ($files) {$cache = file_get_contents($files[0]);return unserialize($cache);}}  public function set($key, $value) {    $this->delete($key);$file = DIR_CACHE . 'cache.' . $key . '.' . (time() + $this->expire);    $handle = fopen($file, 'w');    fwrite($handle, serialize($value));    fclose($handle);  }  public function delete($key) {$files = glob(DIR_CACHE . 'cache.' . $key . '.*');if ($files) {    foreach ($files as $file) {      if (file_exists($file)) {@unlink($file);clearstatcache();}    }}  }}?>