在Phpspreadsheet中如何将数组数据导出为Excel文件并实现行合并？

$data = [
    "customer" => "西卡若卡",
    "product" => [
        [
            "name" => "瓶-500ml塑料瓶",
            "parts" => "24牙35克",
            "rongliang" => "500ml"
        ],
        [
            "name" => "内塞-500ml塑料瓶",
            "parts" => "19小孔内塞+盖板",
        ],
        [
            "name" => "盖子-500ml塑料瓶",
            "parts" => "24牙双层pp盖",
        ],
    ]
];

| 客户   | 产品名称            | 零件            | 容量  |
| ------- | ------------------- | --------------- | ----- |
| 西卡若卡 | 瓶-500ml塑料瓶     | 24牙35克       | 500ml |
|         | 内塞-500ml塑料瓶   | 19小孔内塞+盖板 |       |
|         | 盖子-500ml塑料瓶   | 24牙双层pp盖   |       |

require 'vendor/autoload.php'; //  假设你已通过composer安装了phpspreadsheet

use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();

$sheet->setCellValue('A1', '客户');
$sheet->setCellValue('B1', '产品名称');
$sheet->setCellValue('C1', '零件');
$sheet->setCellValue('D1', '容量');

$row = 2;
$sheet->setCellValue("A{$row}", $data['customer']);

foreach ($data['product'] as $product) {
    $sheet->setCellValue("B{$row}", $product['name']);
    $sheet->setCellValue("C{$row}", $product['parts']);
    $sheet->setCellValue("D{$row}", $product['rongliang'] ?? ''); // 使用空字符串处理缺失的容量
    $row++;
}

// 合并'客户'列的单元格
$sheet->mergeCells("A2:A{$row-1}");

$writer = new Xlsx($spreadsheet);
$writer->save('output.xlsx');