public function lock()
    {
        //Prevent lock take over, only an saved and unlocked row and be locked
        if(!$this->isNew() && !$this->isLocked())
        {
            $this->locked_by = (int) $this->getObject('user')->getId();
            $this->locked_on = gmdate('Y-m-d H:i:s');
            $this->save();
        }

        return true;
    }