bad request 400 error in amazon api access - php

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foreach($parsed_xml->OperationRequest->Errors->Error as $error){
echo "Error code: " . $error->Code . "\r\n";
echo $error->Message . "\r\n"; echo "\r\n";
}
}
function printSearchResults($parsed_xml, $SearchIndex){
print("<table>");
if($numOfItems>0){
foreach($parsed_xml->Items->Item as $current){
print("<td><font size='-1'><b>".$current->ItemAttributes->Title."</b>");
if (isset($current->ItemAttributes->Title)) {
print("<br>Title: ".$current->ItemAttributes->Title);
} elseif(isset($current->ItemAttributes->Author)) {
print("<br>Author: ".$current->ItemAttributes->Author);
} elseif(isset($current->Offers->Offer->Price->FormattedPrice)){
print("<br>Price:".$current->Offers->Offer->Price->FormattedPrice);
}else{
print("<center>No matches found.</center>");
}
}
}
}
if (!isset($params["Timestamp"])) {
$params["Timestamp"] = gmdate('Y-m-d\TH:i:s\Z');
}
ksort($params);
$pairs = array();
foreach ($params as $key => $value) {
array_push($pairs, rawurlencode($key)."=".rawurlencode($value));
}
$canonical_query_string = join("&", $pairs);
$string_to_sign = "GET\n".$endpoint."\n".$uri."\n".$canonical_query_string;
$signature = base64_encode(hash_hmac("sha256", $string_to_sign, $aws_secret_key, true));
$request_url = 'http://'.$endpoint.$uri.'?'.$canonical_query_string.'&Signature='.rawurlencode( $signature);
echo "Signed URL: \"".$request_url."\"";
}
function fetchDataUsingAPI($UniqueBatchId) {
echo $this->firstpageurl;
if( isset($_POST['datafetchresume'])){
$lastbatchdetails = GetTaskLastBatchDetails($_GET['taskid']);
$UniqueBatchId = $lastbatchdetails[0];
$this->firstpageurl = $lastbatchdetails[1];
}else {
$this->firstpageurl = $this->ItemSearch($categorySplit[1],$UniqueBatchId);
}
SaveTaskLastBatchDetails($_GET['taskid'], $UniqueBatchId, $this- >firstpageurl);
return $UniqueBatchId;

Answer 1

Every request needs a signature to be calculated and added to the URL. Check out my PHP function for adding a signature.
Also, use CURL rather than file_get_contents. Even though the API returned a 400 error, it also returned XML with it. That XML probably contains helpful error message. If you use CURL, you can detect the 400 error and still read the contents of the page that was returned. With file_get_contents, a 400 error just returns an error. (My recollection of that may be off, but you'll like CURL better.)
Check here for more info on Amazon API error code
In the PHP code, there are three variables left undefined by me. MY_ASSOCIATE_ID, MY_PUBLIC_KEY, MY_PRIVATE_KEY must be defined by you with appropriate values. The two keys are given to you by amazon. You can, for a while, get them here:
https://portal.aws.amazon.com/gp/aws/securityCredentials
Or check the "My Account" menu at the top of this page and go hunting for your security credentials. The "new and improved" system has been reported to not work with this API, so I would get your two keys from the link above while you still can. Store them in a safe place.
The associate ID can be anything--the API doesn't check it. The API uses uses your URL parameters to generate a signature with your public key, which is included in the URL, and the secret key they have on file associated with the public key you provided. The signature you provide in the URL must match theirs exactly, so your keys and your sig function must exactly match theirs.