php codeigniter，验证空值

我的项目中有这段代码：

public function new_inspection_report() {
                $NOWdate = new Datetime('now');
        $this->check_session();
        $this->restrict_ordinary();
    $truckno = $this->uri->segment(2);
    $data['title'] = "New Inspection Report";
    $data['result'] = $this->truck->find_truckbyid($truckno);
    $data['regno'] = $data['result']['registrationno'];
    $data['odometer'] = $this->truck->validate_odemeter($truckno,$this->input->post('odometerreading'),"mypms_inspection_report");
    $data['lastodometer'] = $data['odometer']['odometerreading'];
    $data['date'] = $this->truck->validate_date($truckno,$this->input->post('datestarted'),"mypms_inspection_report","date");
    $data['lastdate'] = $data['date']['date'];

        $this->load->library('form_validation');
        $this->form_validation->set_error_delimiters("<div class='row'><div class='col-lg-12'><div class='alert alert-danger alert-dismissable'><button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;</button><i class='fa fa-info-circle'></i>&nbsp;", "</div></div></div>");
        $data['validateodometer'] = $this->truck->validate_odemeter($truckno,$this->input->post('odometerreading'),"mypms_inspection_report");
        $data['validatedate'] = $this->truck->validate_date($truckno,$this->input->post('datestarted'),"mypms_inspection_report","date");
        if($this->form_validation->run('new_inspectionreport') === FALSE) {
    $this->load->view('header',$data);
    $this->load->view('new_inspection_report',$data);
    $this->load->view('footer',$data);  
        }else{
            if($this->input->post('odometerreading') < $data['validateodometer']['odometerreading']) {
                            $this->session->set_flashdata('success_insert', "4");
                            redirect(base_url("new-inspection-report/".$truckno));  

                    }else{

                        if($this->input->post('datestarted') < $data['validatedate']['date']) {
                            $this->session->set_flashdata('success_insert', "5");
                            redirect(base_url("new-inspection-report/".$truckno));  
                        }elseif ($this->input->post('datestarted') > $NOWdate)
                        {

                            $this->input->post('datestarted') > $NOWdate;
                            $this->session->set_flashdata('success_insert', "6");
                            redirect(base_url("new-inspection-report/".$truckno));
                        }
                        else
                        {
                        $this->truck->insert_inspectionreport($truckno);
                        $last_id = $this->db->insert_id();
                        $count = $this->truck->count_inspection_bytruck($truckno);
                        $this->authentication->watch_dog("Successfully add inspection report with ID ".$last_id,$this->session->userdata('id'));
                        $this->truck->insert_inspectionno($count,$last_id);

                        $this->session->set_flashdata('success_insert', "1");
                        redirect(base_url('new-inspection-report/'.$truckno));
                        }
                    }
        }
    }

将这些变量传递给我的观点：

    $data['odometer'] = $this->truck->validate_odemeter($truckno,$this->input->post('odometerreading'),"mypms_inspection_report");
    $data['lastodometer'] = $data['odometer']['odometerreading'];
    $data['date'] = $this->truck->validate_date($truckno,$this->input->post('datestarted'),"mypms_inspection_report","date");
    $data['lastdate'] = $data['date']['date'];}

变量 data['里程表'] 在我的 SQL 数据库中获取与 data['date']（日期）相同的最新记录（里程表）。

所以问题是如果"$data['lastodometer']"为空，而'$data['lastdate']'为空（我的数据库中还没有以前的记录），我会收到 Undefined index: odometerreading 和 Message: Undefined index: date 的错误。如果我的日期库上还没有记录，如何将我的寿命计设置为 0 并将 lastdate 设置为 datetoday？