PHP Amazon SDK - s3 putObject始终返回403

Question

我正在尝试集成PHP Amazon SDK - s3 api。我给出了正确的凭据。但我不确定putObject参数。 这是我试过的代码：

  try {
    $s3Client->putObject(array(
      'Bucket' => $bucket,
      'Key'    => $filename,
      'Body'   => file_get_contents(drupal_realpath($file_path)),
      'ACL'         => 'public-read',
    ));
  } catch (S3Exception $e) {echo '<pre>';print_r($e);
        echo "There was an error uploading the file.\n";
  }
  exit;

发出请求后，我收到此回应：

Aws\S3\Exception\AccessDeniedException Object
(
[response:protected] => Guzzle\Http\Message\Response Object
    (
        [body:protected] => Guzzle\Http\EntityBody Object
            (
                [contentEncoding:protected] => 
                [rewindFunction:protected] => 
                [stream:protected] => Resource id #219
                [size:protected] => 
                [cache:protected] => Array
                    (
                        [wrapper_type] => PHP
                        [stream_type] => TEMP
                        [mode] => w+b
                        [unread_bytes] => 0
                        [seekable] => 1
                        [uri] => php://temp
                        [is_local] => 1
                        [is_readable] => 1
                        [is_writable] => 1
                    )

                [customData:protected] => Array
                    (
                    )

            )

        [reasonPhrase:protected] => Forbidden
        [statusCode:protected] => 403
        [info:protected] => Array
            (
                [url] => https://s3.amazonaws.com/my_test/ak1.jpg
                [content_type] => application/xml
                [http_code] => 403
                [header_size] => 273
                [request_size] => 320
                [filetime] => -1
              .........................................................................................................