PHP Excel导出仅显示mysql表中的最后一行

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

$sql = "SELECT * FROM table_name";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        // 处理每一行数据
    }
}

require_once 'PHPExcel/PHPExcel.php';

$objPHPExcel = new PHPExcel();
$objPHPExcel->getActiveSheet()->setCellValue('A1', 'Column 1');
$objPHPExcel->getActiveSheet()->setCellValue('B1', 'Column 2');
// 设置其他列标题

$row = 2;
while ($row_data = $result->fetch_assoc()) {
    $objPHPExcel->getActiveSheet()->setCellValue('A' . $row, $row_data['column1']);
    $objPHPExcel->getActiveSheet()->setCellValue('B' . $row, $row_data['column2']);
    // 设置其他列数据

    $row++;
}

$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save('output.xlsx');

header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment;filename="output.xlsx"');
header('Cache-Control: max-age=0');

$objWriter->save('php://output');