php如何下载上传的文件

<code class="php">$file = $_FILES['myfile'];</code>

<code class="php">if ($file['error'] == 0) {
    // 文件上传成功
} else {
    // 文件上传失败，输出错误信息
    switch ($file['error']) {
        case UPLOAD_ERR_INI_SIZE:
            echo '文件大小超过了 php.ini 中的 upload_max_filesize 设置';
            break;
        case UPLOAD_ERR_FORM_SIZE:
            echo '文件大小超过了表单中 MAX_FILE_SIZE 设置';
            break;
        case UPLOAD_ERR_PARTIAL:
            echo '文件只有部分被上传';
            break;
        case UPLOAD_ERR_NO_FILE:
            echo '没有文件被上传';
            break;
        case UPLOAD_ERR_NO_TMP_DIR:
            echo '没有找到临时目录';
            break;
        case UPLOAD_ERR_CANT_WRITE:
            echo '无法将文件写到磁盘';
            break;
        case UPLOAD_ERR_EXTENSION:
            echo '文件上传被扩展阻止了';
            break;
    }
}</code>

<code class="php">$filePath = $file['tmp_name'];</code>

<code class="php">header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $file['name'] . '"');</code>

<code class="php">readfile($filePath);</code>