如何在php中显示可从mysql的BLOB类型下载的pdf文件？

header('Content-Disposition: attachment; filename="file.pdf"');
header('Content-Type: application/pdf');

<?php
// 连接数据库
$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("连接数据库失败: " . $conn->connect_error);
}

// 查询BLOB字段中的PDF文件数据
$sql = "SELECT pdf_data FROM table_name WHERE id = 1";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    $row = $result->fetch_assoc();
    $pdfData = $row['pdf_data'];

    // 将二进制字符串保存为临时文件
    $tempFile = tempnam(sys_get_temp_dir(), 'pdf');
    file_put_contents($tempFile, $pdfData);

    // 设置下载头部
    header('Content-Disposition: attachment; filename="file.pdf"');
    header('Content-Type: application/pdf');

    // 输出临时文件内容到浏览器
    readfile($tempFile);

    // 删除临时文件
    unlink($tempFile);
} else {
    echo "未找到PDF文件";
}

$conn->close();
?>