6CS028 Workshop - Web Services

Main Page >> Web Application Development >> Workbook >> Week 07

There are so many exciting APIs available on the web that it is impossible to cover them all here… so let’s have a look at a known REST example and a known SOAP example:

• REST - The Amazon API
• SOAP - The Google Search API

A REST example: Amazon

Note that Amazon is one of the rare providers to still offer both REST and SOAP interfaces to their services… let’s have a look at their REST API.

First, let’s simply select the top selling books on Amazon.com

With REST, it's all about calling the right URL, passing in the right parameters... here is the URL for the top selling books on Amazon.com:

Click me!

If you click on the URL, your browser simply display the XML data (try looking at the page's source code).

So our PHP code looks very much like the code we used to access an RSS feed. Indeed in both cases we are accessing a remote XML file!

<H1>Top Selling Books on Amazon.com at <?= date("d-m-Y H:i"); ?></H1>
<?
 
  // My key is 0NR4EHP6HAVW61V6P1G2
  // APPLY FOR YOUR OWN KEY!!
 
  // Node for books
  $node = 283155;
 
  // Build REST url 
  $url = "http://webservices.amazon.com/onca/xml?";
  $url.= "Service=AWSECommerceService&";
  $url.= "SubscriptionId=0NR4EHP6HAVW61V6P1G2&";
  $url.= "Operation=BrowseNodeLookup&";
  $url.= "BrowseNodeId=$node&";
  $url.= "ResponseGroup=TopSellers";

  // Get raw data
  $response = file_get_contents($url);
  
  // Convert raw data to object
  $xml = simplexml_load_string($response);
 
  // Browse object and display book titles
  foreach($xml->BrowseNodes->BrowseNode->TopSellers->TopSeller as $book)
  {
    echo $book->Title."<br>";
  }

?>

And that’s it! Your page should now be displaying the titles of the top selling books.

But what if you want to know more about those books? Well you need to send another request to ask for more details on each book… The following example builds on the previous one, and displays a picture of the book cover next to its title! You could display a lot more (authors, similar books, prices etc…) but we’ll leave that bit up to you.

<H1>Top Selling Books on Amazon.com at <?= date("d-m-Y H:i"); ?></H1>
<?
 
  // My key is 0NR4EHP6HAVW61V6P1G2
  // APPLY FOR YOUR OWN KEY!!
 
  // Node for books
  $node = 283155;
 
  // Build REST url 
  $url = "http://webservices.amazon.com/onca/xml?";
  $url.= "Service=AWSECommerceService&";
  $url.= "SubscriptionId=0NR4EHP6HAVW61V6P1G2&";
  $url.= "Operation=BrowseNodeLookup&";
  $url.= "BrowseNodeId=$node&";
  $url.= "ResponseGroup=TopSellers";
         
  // Get raw data
  $response = file_get_contents($url);
  
  // Convert raw data to object
  $xml = simplexml_load_string($response);
 
  // Put a;; asin numbers into a variable
  $ASIN = "";
  foreach($xml->BrowseNodes->BrowseNode->TopSellers->TopSeller as $book)
  {
    $ASIN = $ASIN.$book->ASIN.",";
  }
 
  // Make second call, asking for more details
  
  $url = "http://webservices.amazon.com/onca/xml?";
  $url.= "Service=AWSECommerceService&";
  $url.= "SubscriptionId=0NR4EHP6HAVW61V6P1G2&";
  $url.= "Operation=ItemLookup&";
  $url.= "ItemId=$ASIN&";
  $url.= "ResponseGroup=Medium";
  
  $response = file_get_contents($url);
  $xml = simplexml_load_string($response);
 
  foreach($xml->Items->Item as $bd)
  {
    $ASIN = $bd->ASIN;
    $image = $bd->MediumImage->URL;
    $url = $bd->DetailPageURL;
    $Title =$bd->ItemAttributes->Title;
 
    echo "<IMG src=\"$image\">";
    echo "$Title<BR>";
    
  }
?>

A SOAP example: Google Search

Accessing SOAP APIs is just as simple. But first you need to download the NuSOAP library. It will do a lot of the work for you.

• http://sourceforge.net/projects/nusoap/files/

Simply unzip the archive in your web pages’ folder.

Now the code… well nothing too difficult here:

• First you include the library you have just downloaded
• Then you create a SOPA client object and set its encoding
• Then you prepare your SOAP request and send it.
• The response is a multidimensional array. You can use the print_r command to display it fully if you wish.

<?
  require("nusoap/lib/nusoap.php");

  // What we are searching for
  $search = "Alix Bergeret";

  // Create soap client
  $client = new soapclient("http://api.google.com/GoogleSearch.wsdl", true);

  // Set encoding
  $client->soap_defencoding = 'UTF-8';

  // Prepare request
  $request = array(
		'key'=>'4B0KufpQFHJxhAxzua0tR11ElLNrHRJ6',
		'q'=>$search,
		'start'=>0,
		'maxResults'=>5,
		'filter'=>false,
		'restrict'=>'',
		'safeSearch'=>true,
		'lr'=>'',
		'ie'=>'',
		'oe'=>'',
	);

  // Send request and read response
  $result = $client->call('doGoogleSearch', $request, "urn:GoogleSearch", "urn:GoogleSearch");

  // Loop through array and display
  foreach($result['resultElements'] as $one_result)
  {
    print "<h1>{$one_result['title']}</h1>";
    print "<p>{$one_result['snippet']}</p>";
  }
?>

All done!