从异步嘎嘎声请求中获取文件扩展名

我正在使用guzzle从url中检索图像。其中一些网址来自 s3。S3 对图像使用application/octet-stream内容类型。我认为我无法访问fulfilled回调中的$request对象，因此我无法看到扩展名是否在 url 中。当内容类型为application/octet-stream时，我有什么办法可以猜测fulfilled回调中的扩展名吗？

<?php
function getExtension(Response $response) {
    $contentType = explode(';', $response->getHeaderLine('Content-Type'), 2)[0];
    $extensions = [
        'image/png' => '.png',
        'image/jpg' => '.jpg',
        'image/jpeg' => '.jpeg',
        'image/gif' => '.gif',
        'image/tiff' => '.tiff',
        'image/bmp' => '.bmp',
        'application/octet-stream' => false
    ];
    return $extensions[$contentType] ?? null;
}
$client = new Client();
$pool = new Pool($client, $requests, [
        'concurrency' => 5,
        'fulfilled' => function ($response) use ($zip) {
            $ext = getExtension($response);
            if (null === $ext) {
                return;
            }
            if (false === $ext) {
                // figure out the extension somehow
                // $ext = ".foobar";
            }
            $id = Uuid::uuid4()->toString();
            $filename = $id . $ext;
            $zip->addFromString($filename, (string)$response->getBody());
        },
        'rejected' => function ($reason, $index) {
            // no-op
        }
    ]
);
$pool->promise()->wait();