PHP wrote a batch Excel import shipment, record

function upExecel(){
        include 'data/extend/phpexcel_classes/PHPExcel.php';
        / / Determine whether the form to upload is selected
        if (empty($_POST['myfile'])) {
            echo "<script>alert(You did not select a table);history.go(-1);</script>";
        }
        //Get the size of the table, limit the size of the uploaded table to 5M
        $file_size = $_FILES['myfile']['size'];
        if ($file_size>5*1024*1024) {
            echo "<script>alert('Upload failed, the uploaded form cannot exceed 5M size');history.go(-1);</script>";
            exit();
        }
        // Restrict upload form types
        $file_name = $_FILES['myfile']['name'];
            //application/vnd.ms-excel is the xls file type
        $extension = strtolower( pathinfo($file_name, PATHINFO_EXTENSION) );

        // Determine if the form is uploaded successfully
        if (is_uploaded_file($_FILES['myfile']['tmp_name'])) {

            //Receive the excel sheet stored in the cache
            $filename = $_FILES['myfile']['tmp_name'];
            if ($extension =='xlsx') {
                $objReader = \PHPExcel_IOFactory::createReader('Excel2007');//use excel2007 for 2007 format
                $objPHPExcel = $objReader ->load($filename);
            } else if ($extension =='xls') {
                $objReader = \PHPExcel_IOFactory::createReader('Excel5');//use excel2007 for 2007 format
                $objPHPExcel = $objReader ->load($filename);
            }
            //$objPHPExcel = $objReader->load($filename); //$filename can be the uploaded form, or the specified form
            $sheet = $objPHPExcel->getSheet(0);
            $highestRow = $sheet->getHighestRow(); // Get the total number of rows
            // $highestColumn = $sheet->getHighestColumn(); // Get the total number of columns
            / / Loop to read the excel sheet, read one, insert one
            //j indicates which line to start reading from the second line, because the first line is the title and is not saved
            /*if ($shipping_type == 1) {
                $res = $order_service->orderDelivery($order_id, $order_goods_id_array, $express_name, $shipping_type, $express_company_id, $express_no,$suppliercode);*/
            $order_service = new OrderService();
            $express = new NsOrderExpressCompanyModel();
            $num = 0;
            for($j=2;$j<=$highestRow;$j++)
            {
                $a = $objPHPExcel->getActiveSheet()->getCell("A".$j)->getValue();//order_id
                $b = $objPHPExcel->getActiveSheet()->getCell("B".$j)->getValue();//order_goods_id
                $c = $objPHPExcel->getActiveSheet()->getCell("C".$j)->getValue();//express_name
                $d = $objPHPExcel->getActiveSheet()->getCell("D".$j)->getValue();//express_no

                $express_id = $express->where('company_name',$c)->value('co_id');
                if(!$express_id || !is_numeric($d)){
                    echo "<script>alert('The courier company name or tracking number on line ".$j." is incorrect');window.location.href='/admin/spell/countspellgroup';</script>";
                    break;
                }
                $res = $order_service->orderDelivery($a, $b, $c, 1, $express_id,$d,'');
                // exit();
                Db::execute("insert into ns_wxmsg_spellgroup(orderid,msgtype,addtime,senttime,status) (select order_id,'10',".time().",0,'' from ns_spellgroup where pay_time>0 and order_id=".$a.")");
                $num++;
            }
            if ($num) {
                echo "<script>alert($num.'Line data added successfully!');window.location.href='/admin/spell/countspellgroup';</script>";
            }
        }
    }

I just started writing PHP, and there are many shortcomings. Please correct me. I wanted to write a transaction, but I haven't done it yet, so I used it first, and I will optimize it later.