Amazon product advertising APIを使ってWordpressのサイドバーにリンクを表示するためのサンプルコード。

amazon_widget_sample.php

<?php

function create_url($params,$aws_secret_key) {
	 // The region you are interested in
	 $endpoint = "webservices.amazon.co.jp";

	 $uri = "/onca/xml";

	 // Set current timestamp if not set
	 if (!isset($params["Timestamp"])) {
    	    $params["Timestamp"] = gmdate('Y-m-d\TH:i:s\Z');
	 }

	 // Sort the parameters by key
	 ksort($params);

	 $pairs = array();

	 foreach ($params as $key => $value) {
    	 	 array_push($pairs, rawurlencode($key)."=".rawurlencode($value));
	 }

	 // Generate the canonical query
	 $canonical_query_string = join("&", $pairs);

	 // Generate the string to be signed
	 $string_to_sign = "GET\n".$endpoint."\n".$uri."\n".$canonical_query_string;

	 // Generate the signature required by the Product Advertising API
	 $signature = base64_encode(hash_hmac("sha256", $string_to_sign, $aws_secret_key, true));

	 // Generate the signed URL
	 $request_url = 'http://'.$endpoint.$uri.'?'.$canonical_query_string.'&Signature='.rawurlencode($signature);

	 // echo "Signed URL: \"".$request_url."\"";
	 return $request_url;
}

function parse_response($response,$http_response_header,$i) {
	 $rcode = 0;
	 foreach($http_response_header as $k=>$v) {
  	    if (preg_match("#HTTP/[0-9\.]+\s+([0-9]+)#",$v,$out)) {
	       $rcode = intval($out[1]);
  	    }
	 }

	 if ($rcode >= 300) {
	    return "";
	 }

	 $parsed_xml = null;

	 if (isset($response)) {
   	    $parsed_xml = simplexml_load_string($response);
	 }

	 $content = "";

	 $items = array();

	 if ($response && isset($parsed_xml) && !$parsed_xml->faultstring && !$parsed_xml->Items->Request->Errors) {
    	    foreach ($parsed_xml->Items->Item as $current) {
	    	    $item = array();
		    $item["DetailPageURL"] = $current->DetailPageURL;
		    $item["Title"] = $current->ItemAttributes->Title;
		    $item["Publisher"] = $current->ItemAttributes->Publisher;
		    if (isset($current->ItemAttributes->EAN)) {
		       $item["EAN"] = $current->ItemAttributes->EAN;
		    } else {
		       $item["Price"] = $current->ItemAttributes->ListPrice->FormattedPrice;
		    }
		    $item["Feature"] = $current->ItemAttributes->Feature;
		    $item["ImageURL"] = $current->MediumImage->URL;
		    $items[] = $item;
    	    }
	 }

	 //var_dump($items);
	 if (count($items) == 0) {
	    return "";
	 }
	 return $items[mt_rand(0,count($items))];
}

function get_card() {
	 global $wpdb;
	 
	 $cards = array();

	 // First, I try to get card on the database.
	 $card_rows = $wpdb->get_results("select card_for_index,card_for_page from link_cache where generated_at < NOW() and generated_at > SUBDATE(NOW(), INTERVAL 3600 SECOND)",ARRAY_A);

	 if (count($card_rows) != 0) {
	    $cards["index"] = $card_rows[0]["card_for_index"];
	    $cards["page"] = $card_rows[0]["card_for_page"];
	    return $cards;
	 }

	 // Get some keys from the database.
	 $key_rows = $wpdb->get_results("鍵の読みだし用のSQL文",ARRAY_A);
	 if (count($key_rows) != 0) {
	    $aws_access_key_id = $key_rows[0]["アクセスキー"];
	    $aws_secret_key = $key_rows[0]["秘密鍵"];
	    $amazon_associate_id = $key_rows[0]["アソシエイトID"];
	 } else {
	    return '';
	 }

	 $rows = $wpdb->get_results("select search_term from amazon_product_link where search_term is not null and disabled=0 order by rand() limit 0,1",ARRAY_A);

	 if (count($rows)==0) {
   	    //echo "No rows. Abort here!\n";
  	    return '';
	 }

	 $kws = $rows[0]['search_term'];

	 $params = array(
    	 	 "Service" => "AWSECommerceService",
    		 "Operation" => "ItemSearch",
    		 "AWSAccessKeyId" => $aws_access_key_id,
    		 "AssociateTag" => $amazon_associate_id,
    		 "SearchIndex" => "All",
    		 "ResponseGroup" => "Images,ItemAttributes,Offers",
    		 "Keywords" => $kws
	 );

	 //echo "Keywords:".$kws."\n";

	 $context = stream_context_create(array(
	 	  'http' => array('ignore_errors' => true)));

	 $response = file_get_contents(create_url($params,$aws_secret_key),false,$context);

	 $pos = strpos($http_response_header[0], '200');

	 if ($pos === FALSE) {
	    // Workaround against an error.
	    $card_rows = $wpdb->get_results("select card_for_index,card_for_page from link_cache order by id desc limit 0,1",ARRAY_A);

	    if (count($card_rows) != 0) {
	       $cards["index"] = $card_rows[0]["card_for_index"];
	       $cards["page"] = $card_rows[0]["card_for_page"];
	       return $cards;
	    }
   	    return '';
	 }

	 $item = parse_response($response,$http_response_header,1);

	 if ($item === "") {
	    return '';
	 }

	 $ean = '';
	 if (isset($item["EAN"])) {
	    $ean = 'EAN: '.$item["EAN"].'<br/>';
	 }
	 $price = '';
	 if (isset($item["Price"])) {
	    $price = 'Price: '.$item["Price"].'<br/>';
	 }

	 if (!isset($item["Title"])) {
	    error_log("Error! keyword=".urlencode($kws),0);
	    return '';
	 }

	 $feature_str = "";
	 $feature_max_count = 4;
	 $feature_count = 0;
	 if (count($item["Feature"]) > 0) {
	    $feature_str .= '<div style="border-top-style: solid;border-color: #1E3E8A;margin-top:4px;border-width:1px;padding-top:4px;text-align:left;">';
	    foreach ($item["Feature"] as $feature) {
	       if ($feature_count < $feature_max_count) {
	          $feature_str .= $feature."<br/>";
	       }
	       $feature_count++;
	    }
	    $feature_str .= '<br/><a href="'.$item["DetailPageURL"].'"><span style="color: #1E3E8A;font-size:85%;">Read more&gt;&gt;</span></a>';
	    $feature_str .= '</div>';
	 }

	 $cards["index"] = '<div style="width:305px;text-align:center;margin: 0 auto;">
	     <a href="'.$item["DetailPageURL"].'"><img src="'.$item["ImageURL"].'" align="left" style="margin-right:10px;margin-bottom:5px;"/></a><div style="margin-bottom:5px;"><a href="'.$item["DetailPageURL"].'"><span style="color:#1E3E8A;font-weight:bold;font-size:110%;">'.$item["Title"].'</span></a></div><br/>'.$item["Publisher"].'<br/>'.$ean.$price.$feature_str.'
	     <br clear="left"/>
	     </div>
	     <div class="clear"></div>';
	 $cards["page"] = "";

	 $wpdb->query("insert into link_cache(card_for_index,card_for_page) values('".$cards["index"]."','".$cards["page"]."')");

	 return $cards;
}
?>