You can use a comma-separated list of ASINS in your requests to get up to 10 ASINs at once. Also look into "batch-request" with which you can double the number of products returned by the API.
In addtion, do not forget to implement caching, so that frequent accesses to certain pages do not result in the same API requests over and over again.

Correct. I've already mentioned this in a previous comment. Please note that the associate tag should be a valid one, so you have to create an an Amazon Associate account.

Es sollte mit den genannten Änderungen auch für .de funktionieren. Wenn Sie möchten, können Sie mir Ihr Script einmal per Email schicken. Vll. finden wir dann den Fehler.

Please look at my answer to a similar question: http://mierendo.com/software/aws_signed_query/#ID...

Bitte probieren Sie die Modifikationen die ich in folgender Antwort beschrieben habe: http://mierendo.com/software/aws_signed_query/#ID...

The generation of the signature is still working but you may have to modify a few things so that the complete functions continues to work with the updated version of the API:

1. Replace
$host = "ecs.amazonaws.".$region;
with
$host = 'webservices.amazon.'.$region;

2. Replace
$params["Version"] = "2009-03-31";
with
$params["Version"] = "2011-08-01";

3. Make sure that you add a parameter named "AssociateTag" with your Amazon Associate Tag as the value to your list of parameters for each request.

With these modifications it should continue to work. I will soon upload an updated version of the script.

Please try to use a response group like "Large" and look at the complete XML response. If it does contain these details you will not be able to extract them via the API. If your request works you can then try to limit your response group to something smaller than "Large" to save bandwidth and to speed up your requests.

If an error occurs, the XML will contain an error message. You can extract that from the XML response. For the exact structure of the error messages, please look at the documentation: http://docs.amazonwebservices.com/AWSECommerceSer...

Regarding the private key: I think this is the correct way to construct the key. Just try if it works. If not, it could be possible that you got multiple private/public key pairs from Amazon and that this was the wrong one.

Yes, you should cache the response, because the number of allowed requests per hour is limited. Make sure to read the Product Advertising API License Agreement, it tells you how long you are allowed to cache the data.

Please replace "ecs.amazonaws.".$region with "webservices.amazon.".$region. $region should be "it" in your case. I will update the script soon.
Does this work for you?