当我想要使用twitter api更新个人资料横幅时，它会提供未知类型的鞋子图像

我正在使用twitter api更新横幅。我的api请求如下

$url = 'https://api.twitter.com/1.1/account/update_profile_banner.json';
$requestMethod = 'POST';

$postfields = array(
    'width' => 520,
    'height'=> 260,
'banner' => $encoded_data
);

$twitter = new TwitterAPIExchange($settings);
echo $twitter->buildOauth($url, $requestMethod)
             ->setPostfields($postfields)
             ->performRequest();

"{"request":"\/1.1\/account\/update_profile_banner.json","error":"Image with unknown type provided"}" 

当我发送请求时，它会显示一个错误，如bellow

$url = 'https://api.twitter.com/1.1/account/update_profile_banner.json';
$requestMethod = 'POST';

$postfields = array(
    'width' => 520,
    'height'=> 260,
'banner' => $encoded_data
);

$twitter = new TwitterAPIExchange($settings);
echo $twitter->buildOauth($url, $requestMethod)
             ->setPostfields($postfields)
             ->performRequest();

"{"request":"\/1.1\/account\/update_profile_banner.json","error":"Image with unknown type provided"}" 

现在让我看看这里出了什么问题

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谢谢

您如何对这些数据进行编码<代码>$encoded_数据