Amazon Products API in Custom WordPress Plugin without cURL (currently working outside WP)

I post a lot of products on my blog that link back to Amazon with the affiliate program. I currently use a custom plugin to format the items in a post/page. It has attributes for the target URL, tracking image src and then my own custom sizing for each list as well as my own description and product image.

The reason I have a custom plugin like this is because it's a fundamental module that I also use for other items such as posting YouTube videos and links to other posts. It makes the whole design very consistent and easy to manage.

I do not want to use an existing Amazon product plugin, because it would involve double maintenance in styling and updating the code.

I have the following code (sourced heavily from http://ift.tt/1uAg2k8) which is working as needed in my standard local development server (non-WordPress). When I place it into WordPress as a plugin to use as a shortcode, I clearly have an error because the page loads up until the point of outputting the code. If I remove all instances of querying the Amazon database, my shortcode functions as expected. WP_Debug is showing no errors either...

I have read about the problems of using cURL in WordPress plugins, so I am looking to replace that with something like WP_Http using wp_remote_get(), however I am struggling to get a working version and unsure how to use it.

Any help would be greatly appreciated!

The code:

I believe the problem lies mainly within the getPage() function. As I mentioned, this code works perfectly fine outside of WordPress on the same localhost.

$response = getAmazonPrice("co.uk", "B00D93QR9I");

function getAmazonPrice($region, $asin) {

    $xml = aws_signed_request($region, array(
        "Operation" => "ItemLookup",
        "ItemId" => $asin,
        "IncludeReviewsSummary" => False,
        "ResponseGroup" => "Medium,OfferSummary"
    ));

    $item = $xml->Items->Item;
    $title = htmlentities((string) $item->ItemAttributes->Title);
    $url = htmlentities((string) $item->DetailPageURL);
    $image = htmlentities((string) $item->MediumImage->URL);
    $price = htmlentities((string) $item->OfferSummary->LowestNewPrice->Amount);
    $code = htmlentities((string) $item->OfferSummary->LowestNewPrice->CurrencyCode);
    $qty = htmlentities((string) $item->OfferSummary->TotalNew);

    if ($qty !== "0") {
        $response = array(
            "code" => $code,
            "price" => number_format((float) ($price / 100), 2, '.', ''),
            "image" => $image,
            "url" => $url,
            "title" => $title
        );
    };

    return $response;

};

function getPage($url) {

    $curl = curl_init($url);
    curl_setopt($curl, CURLOPT_FAILONERROR, true);
    curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
    $html = curl_exec($curl);
    curl_close($curl);

    return $html;
};

function aws_signed_request($region, $params) {

    $public_key = "XXX_REMOVED"; // Public Key Here
    $private_key = "XXX_REMOVED"; // Secret Key Here

    $method = "GET";
    $host = "ecs.amazonaws." . $region;
    $host = "webservices.amazon." . $region;
    $uri = "/onca/xml";

    $params["Service"] = "AWSECommerceService";
    $params["AssociateTag"] = "XXX_REMOVED"; // Put your Affiliate Code here
    $params["AWSAccessKeyId"] = $public_key;
    $params["Timestamp"] = gmdate("Y-m-d\TH:i:s\Z");
    $params["Version"] = "2011-08-01";

    ksort($params);

    $canonicalized_query = array();
    foreach ($params as $param => $value) {
        $param = str_replace("%7E", "~", rawurlencode($param));
        $value = str_replace("%7E", "~", rawurlencode($value));
        $canonicalized_query[] = $param . "=" . $value;
    };

    $canonicalized_query = implode("&", $canonicalized_query);

    $string_to_sign = $method . "\n" . $host . "\n" . $uri . "\n" . $canonicalized_query;
    $signature = base64_encode(hash_hmac("sha256", $string_to_sign, $private_key, True));
    $signature = str_replace("%7E", "~", rawurlencode($signature));

    $request = "http://" . $host . $uri . "?" . $canonicalized_query . "&Signature=" . $signature;
    $response = getPage($request);

    var_dump($response); // Currently not displaying anything

    $pxml = @simplexml_load_string($response);
    if ($pxml === False) {
        return False;// no xml
    } else {
        return $pxml;
    };
};
// END CODE FROM http://ift.tt/1uAg2k8