I have this function in PHP in Windows with easyPHP to sign a request for Amazon's Product Advertising API but doesn't work, because the output doesn't generate a correct signature and I don't know why. When I make the request with the generate url, Amazon says that the SignatureDoesNotMatch
function amazon_get_signed_url($searchTerm) {
$keyword = $searchTerm; // The keywords you're searching for
$aws = array();
$keyword = urlencode($keyword);
$url = "http://webservices.amazon.com/onca/xml?Service=AWSECommerceService";
$url .= "&AWSAccessKeyId=".AWS_ACCESS_KEY_ID;
$url .= "&Operation=ItemSearch";
$url .= "&SearchIndex=DVD";
$url .= "&Keywords=".$keyword."";
$url .= "&ResponseGroup=Small,OfferFull,Images,Reviews,ItemAttributes,SalesRank";
$url .= "&Timestamp=".gmdate('Y-m-d\TH:i:s\Z');
$url = str_replace("+",urlencode("+"),$url);
$url_a = parse_url($url);
$url_a['query'] = str_replace(',',urlencode(','),$url_a['query']);
$url_a['query'] = str_replace(';',urlencode(':'),$url_a['query']);
parse_str($url_a['query'],$params);
uksort($params, 'strnatcmp');
$qstr = '';
foreach ($params as $key => $val) {
$qstr .= "=".rawurlencode($val);
}
$qstr = substr($qstr, 1);
$qstr = str_replace('%20',urlencode('+'),$qstr);
$qstr = str_replace(',',urlencode(','),$qstr);
$qstr = str_replace(';',urlencode(':'),$qstr);
$sig = "GET\nwebservices.amazon.com\n/onca/xml\n".$qstr;
$sig = base64_encode(hash_hmac('sha256', $sig, AWS_SECRET_ACCESS_KEY, true));
$sig = str_replace('+','%2B',$sig);
$sig = str_replace('=','%3D',$sig);
$params['Signature'] = $sig;
$p = array();
foreach($params as $k=>$v) {
$p[]=$k."=".$v;
}
$qstr = implode("&",$p);
$rebuilt_url = $url_a['scheme']."://".$url_a['host'].$url_a['path']."?".$qstr;
$aws['url'] = $url."&Signature=".$sig;
return $aws['url'];
}
