code: public function Drop($key) {
  		if(!$this->IsPathValid()) return;
  
  		$file = $this->GetFileName($key);
  		if(file_exists($file)) {
  			if(!is_writable($file)) {
  				/*//todo/
  				log this error.
  				//*/
  				echo "Unable to remove cache {$file}", PHP_EOL;
  			} else {
  				unlink($file);
  			}
  		}
  
  		return;
  	}
docs: //////////////