if (!isset($last_update) && in_array($this->status, array('ok','readonly'))) {
$last_cmd = $this->rrdtool_bin.' last '.$this->rrd_file;
$return = trim(`$last_cmd 2>&1`);
$last_update = is_numeric($return)?$return:null;
if (!isset($last_update) && in_array($this->status, array('ok','readonly'))) {
$last_cmd = $this->rrdtool_bin.' last '.$this->rrd_file;
$return = trim(`$last_cmd 2>&1`);
$last_update = is_numeric($return)?$return:null;