protected function save( $data ){
		if( !$this->cacheFile )
			return;
		$last	= array(
			'ip'		=> $this->lastIp,
			'timestamp'	=> $this->lastCheck
		);
		$data	= array_merge( $last,  $data );
		return FS_File_Writer::save( $this->cacheFile, json_encode( $data ) );
	}