aws_signed_comprehend.php

<?php
require __DIR__.'/../vendor/autoload.php';


# ************* REQUEST VALUES *************
$method = "POST";
$service = "comprehend";
$region = "us-west-2";
$host = $service . "." . $region . ".amazonaws.com";
$endpoint = "https://" . $host . "/";

# POST requests use a content type header. For Amazon Translate,
# the content is JSON.
$content_type = "application/x-amz-json-1.1";
# Amazon Translate requires an x-amz-target header that has this format:
#     AWSShineFrontendService_20170701.<operationName>.
$amz_target = "Comprehend_20171127.DetectSentiment";

# Pass request parameters for the TranslateText operation in a JSON block.
$request_parameters = '{"Text": "Amazon.com, Inc. is located in Seattle, WA and was founded July 5th, 1994 by Jeff Bezos, allowing customers to buy everything from books to blenders. Seattle is north of Portland and south of Vancouver, BC. Other notable Seattle - based companies are Starbucks and Boeing.", "LanguageCode": "en"}';

# The following functions derive keys for the request. For more information, see
# http://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-python.
function sign($key, $msg){
    $msg_encoded = utf8_encode($msg);
    return hash_hmac('sha256', $msg_encoded, $key, true);
}

function getSignatureKey($key, $date_stamp, $regionName, $serviceName){
    $kDate = sign(utf8_encode("AWS4" . $key), $date_stamp);
    $kRegion = sign($kDate, $regionName);
    $kService = sign($kRegion, $serviceName);
    $kSigning = sign($kService, "aws4_request");
    return $kSigning;
}



# Python can read the AWS access key from environment variables or the configuration file.
# In this example, keys are stored in environment variables. As a best practice, do not
# embed credentials in code.
$access_key = getenv('AWS_ACCESS_KEY_ID');
$secret_key = getenv('AWS_SECRET_ACCESS_KEY');


# Create a date for headers and the credential string
$t = new DateTime('UTC');
$amz_date = $t->format('Ymd\THis\Z'); //t.strftime("%Y%m%dT%H%M%SZ")
$date_stamp = $t->format('Ymd'); //t.strftime("%Y%m%d")  # Date w/o time, used in credential scope


# ************* TASK 1: CREATE A CANONICAL REQUEST *************
# For information about creating a canonical request, see http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html.

# Step 1: Define the verb (GET, POST, etc.), which you have already done.

# Step 2: Create a canonical URI. A canonical URI is the part of the URI from domain to query.
# string (use '/' if no path)
$canonical_uri = "/";

## Step 3: Create the canonical query string. In this example, request
# parameters are passed in the body of the request and the query string
# is blank.
$canonical_querystring = "";

# Step 4: Create the canonical headers. Header names must be trimmed,
# lowercase, and sorted in code point order from low to high.
# Note the trailing \n.
$canonical_headers = 
    "content-type:"
    . $content_type
    . "\n"
    . "host:"
    . $host
    . "\n"
    . "x-amz-date:"
    . $amz_date
    . "\n"
    . "x-amz-target:"
    . $amz_target
    . "\n"
;


# Step 5: Create the list of signed headers by listing the headers
# in the canonical_headers list, delimited with ";" and in alphabetical order.
# Note: The request can include any headers. Canonical_headers and
# signed_headers should contain headers to include in the hash of the
# request. "Host" and "x-amz-date" headers are always required.
# For Amazon Translate, content-type and x-amz-target are also required.
$signed_headers = "content-type;host;x-amz-date;x-amz-target";

# Step 6: Create the payload hash. In this example, the request_parameters
# variable contains the JSON request parameters.
// payload_hash = hashlib.sha256(request_parameters.encode()).hexdigest()
$payload_hash = hash('sha256', utf8_encode($request_parameters));
# Step 7: Combine the elements to create a canonical request.
$canonical_request = 
    $method
    . "\n"
    . $canonical_uri
    . "\n"
    . $canonical_querystring
    . "\n"
    . $canonical_headers
    . "\n"
    . $signed_headers
    . "\n"
    . $payload_hash;


# ************* TASK 2: CREATE THE STRING TO SIGN*************
# Set the algorithm variable to match the hashing algorithm that you use, either SHA-256 (recommended) or SHA-1.
#
$algorithm = "AWS4-HMAC-SHA256";
$credential_scope = $date_stamp . "/" . $region . "/" . $service . "/" . "aws4_request";
$string_to_sign = 
    $algorithm
    . "\n"
    . $amz_date
    . "\n"
    . $credential_scope
    . "\n"
    . hash('sha256', utf8_encode($canonical_request));


# ************* TASK 3: CALCULATE THE SIGNATURE *************
# Create the signing key using the getSignaturKey function defined above.
$signing_key = getSignatureKey($secret_key, $date_stamp, $region, $service);

# Sign the string_to_sign using the signing_key.

$signature = hash_hmac('sha256', utf8_encode($string_to_sign), $signing_key);


# ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
# Put the signature information in a header named Authorization.
$authorization_header = 
    $algorithm
    . " "
    . "Credential="
    . $access_key
    . "/"
    . $credential_scope
    . ", "
    . "SignedHeaders="
    . $signed_headers
    . ", "
    . "Signature="
    . $signature;

# For Amazon Translate, the request can include any headers, but it must include "host," "x-amz-date,"
# "x-amz-target," "content-type," and "Authorization" headers. Except for the authorization
# header, the headers must be included in the canonical_headers and signed_headers values, as
# noted earlier. Header order is not significant.
# Note: The Python 'requests' library automatically adds the 'host' header.
$headers = array(
    "Content-Type"=> $content_type,
    "X-Amz-Date"=> $amz_date,
    "X-Amz-Target"=> $amz_target,
    "Authorization"=> $authorization_header,
);

// print_r($headers);
// exit;
use GuzzleHttp\Client as GuzzleClient;

$client = new GuzzleClient([
    'headers' => $headers
]);


$body = $request_parameters;

$r = $client->request('POST', $endpoint, [
    'body' => $request_parameters
]);
$response = $r->getBody()->getContents();

echo $response;