Twitter API から「不正な認証データ」(エラー 215) が発生するのはなぜですか?

<code class="php">$token = 'YOUR_TOKEN';
$token_secret = 'YOUR_TOKEN_SECRET';
$consumer_key = 'CONSUMER_KEY';
$consumer_secret = 'CONSUMER_SECRET';

$host = 'api.twitter.com';
$method = 'GET';
$path = '/1.1/followers/ids.json'; // api call path

$query = array( // query parameters
    'cursor' => '-1',
    'screen_name' => 'username'
);

$oauth = array(
    'oauth_consumer_key' => $consumer_key,
    'oauth_token' => $token,
    'oauth_nonce' => (string)mt_rand(), // a stronger nonce is recommended
    'oauth_timestamp' => time(),
    'oauth_signature_method' => 'HMAC-SHA1',
    'oauth_version' => '1.0'
);

// complete the OAuth 1.0 authentication process
// ...

// continue with making the API call</code>