Twitter API エラー コード 215: 「不正な認証データ」が表示されるのはなぜですか?

<code class="php">$consumer_key = 'YOUR_CONSUMER_KEY';
$consumer_secret = 'YOUR_CONSUMER_SECRET';
$access_token = 'YOUR_ACCESS_TOKEN';
$access_token_secret = 'YOUR_ACCESS_TOKEN_SECRET';

// Generate OAuth signature
$oauth_params = array(
    'oauth_timestamp' => time(),
    'oauth_nonce' => uniqid(),
    'oauth_version' => '1.0',
    'oauth_signature_method' => 'HMAC-SHA1'
);
$base_url = 'https://api.twitter.com/1.1/followers/ids.json';
$encoded_url = rawurlencode($base_url);
$encoded_parameters = rawurlencode(http_build_query($oauth_params));
$signature_base = "$method&amp;$encoded_url&amp;$encoded_parameters";
$signature_key = "$consumer_secret&amp;$access_token_secret";
$signature = rawurlencode(base64_encode(hash_hmac('sha1', $signature_base, $signature_key, true)));

// Construct the authorization header
$authorization = "OAuth oauth_consumer_key=\"$consumer_key\", oauth_nonce=\"$oauth_params[oauth_nonce]\", oauth_signature=\"$signature\", oauth_signature_method=\"$oauth_params[oauth_signature_method]\", oauth_timestamp=\"$oauth_params[oauth_timestamp]\", oauth_version=\"$oauth_params[oauth_version]\"";

// Build the request header
$headers = array(
    'Authorization: ' . $authorization
);</code>