Calcular signature - LIB em PHP

Lib em PHP construída e fornecida por um Developer Partner da Amazon para acelerar seu desenvolvimento:

PHP

<? phpclassAmazon
{
    public function calculateAwsSignatureAndReturnHeaders($host, $uri, $requestUrl, $accessKey, $secretKey, $region, $service, $httpRequestMethod, $data, $debug = true)
    {
        $terminationString = 'aws4_request';
        $algorithm = 'AWS4-HMAC-SHA256';
        $hpAlgorithm = 'sha256';
        $canonicalURI = $uri;
        $canonicalQueryString = '';
        $signedHeaders = 'content-type;host;x-amz-date';
        $currentDateTime = new DateTime('UTC');
        $reqDate = $currentDateTime->format('Ymd');
        $reqDateTime = $currentDateTime->format('Ymd\THis\Z');
        $credentialScope[] = $terminationString;
        $credentialScopeStr = implode('/', $credentialScope); 
        $signature = hash_hmac($hpAlgorithm, $stringToSignStr, $kSigning);
        $headers = curl_getinfo($curl, CURLINFO_HEADER_OUT);
        echo "<h5>Request</h5>";
        echo "<pre>";
        echo $headers;
        echo "</pre>";
    }
    curl_close($curl);
    if ($err)
    {
        if ($debug)
        {
            echo "<h5>Error:" . $responseCode . "</h5>";
            echo "<pre>";
            echo $err;
            echo "</pre>";
        }
    }
    else
    {
        if ($debug)
        {
            echo "<h5>Response:" . $responseCode . "</h5>";
            echo "<pre>";
            echo $response;
            echo "</pre>";
        }
    }
    return array(
        "responseCode" => $responseCode,
        "response" => $response,
        "error" => $err
    );
}