Slim 4上传PNG文件在Heroku上不起作用

Question

我正在使用slim和siriusphp upload库在heroku上创建一个简单的上传终结点。在本地，一切正常，但是当我在heroku上部署它时，我的应用程序日志中会出现此错误

PHP Fatal error:  Uncaught RuntimeException:  is not a valid uploaded file in /app/vendor/slim/psr7/src/UploadedFile.php:165

仅当我尝试上载png的png文件时，才会出现此错误。关于如何解决它有任何想法吗？

PHP代码

$app->post('/compress', function(Request $request, Response $response){
    $uploadHandler = new UploadHandler(TMPDIR);

    $args = $request->getParsedBody();
    $payload = $args["payload"];
    
    $uploadHandler->addRule('extension', ['allowed' => ['jpg', 'jpeg', 'png']]);

    $result = $uploadHandler->process( $request->getUploadedFiles() );
    
    // handle single input with single file upload
    if( $result->isValid() ){
        $result->confirm();
        
        $output = bin2hex(random_bytes(8)).'.png';
        $result->clear();
        
        $url = ["processed_image_url" => TMPDIR.$output];
        $data = json_encode($url);

        $response->getBody()->write($data);
    }
    
    return $response;
});