What is a Web Service?
· Docum. Web services: WSDL
Examples of Web Service
· Weather Service
· UPS Web Service
· Credit Card Validation
Web service methods
XML Parsing
Web Service exercises
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45. Introduction to Web services

What is a Web Service?  (click any heading below to return here)

"self-contained, self-describing, modular applications that can be published, located, and invoked across the Web. Once a Web service is deployed, other applications (and other Web Services) can discover and invoke the deployed service."

Web services make software functionality available over the Internet. In other words, let someone at another computer run a program you have on your computer. That way Web applications written in PHP and ASP.Net, can make a request to a program running on another server (the Web service) and use that program's response in a Web site or other application. Web Services perform functions, which can be anything from simple requests to complicated business processes.

Thanks to Phil Namoc, Jason Lien and Brian Ellison for this page.

Documenting Web Services: WSDL

The Web Services Description Language (WSDL) grammar is expressed in XML. WSDL describes Web services, including: interface and end points (or ports), what a service can do, where it resides and how to invoke it via machine-understandable terms targeted for automated distributed communications between Web applications. Simply, a WSDL definition describes how to access a Web service and what operations it will perform.

Examples of Web services

Web Services can vary in function from simple operations like the retrieval of a stock quote, to complex business systems, which access and combine information from multiple sources. Other examples of web services are:

  • validating a credit card
  • retrieving a shipping cost
  • getting a weather forecast
  • translating foreign languages

Web services work with standard Web protocols - XML, HTTP and TCP/IP. A simple Web service process can be described by the following.

  • the Web service provider defines a format for requests for its service and the response the service will generate
  • your computer makes a request for the Web services across the network
  • the Web service performs some action and sends back a response

In the following three examples below, we will be looking at:

  1. a weather service that returns temperatures*
  2. a simple UPS web service to determine shipping rates
  3. a credit card validation web service

The weather example is interesting because your page that shows the temperature does not have to have any JavaScript, or server scripting; simple HTML does the whole job. If you can show an image then you can get the weather. The image attribute src carries the location parameter (temp.php?zip=32507) to the Web service so it will know what region you want the temperature for.

Weather Service

The temperature below is not data in the usual sense. It is an image. The HTML image tag is capable of remote calls to servers to request images, of course, and it can conveniently call for a Web service as well. The service just has to return its information in the form of an image, not text.

This is a common HTML image tag:
<img src="http://www.any.com/picture.jpg" width="10" height="30" alt="pic" />
This is a Web Service HTML image tag:
<img src="http://www.any.com/temp.php?zip=32507" alt="pic" />

If you want to create a Web Service written in PHP that returns images you should start learning about GD which was used to create the example above. The source code for the temperature example is below.

   header("Content-type: image/jpeg");
   $im = imagecreate(100, 20);
   $bg = imagecolorallocate($im, 255, 255, 255);
   $textcolor = imagecolorallocate($im, 0, 0, 0);
   $randval = rand(32,90);
   imagestring($im, 5, 0, 0, $randval." degrees", $textcolor);
   ImageDestroy ($im);

UPS Web Service

This web service allows users to enter in the weight of their package in pounds and select a shipping method.

Select Shipping

By clicking OK, the data request is sent to a server script (receiveUPS.php). This script looks up the corresponding shipping rate in a text file database (receiveUPS.txt). The first field is the method type (UPSGround, Next Day Air, etc.). The second field is the shipping destination country (1 for USA, 2 for Canada, and 3 for World Wide). The third field is shipping rate in dollars. And the fourth field is the package weight in pounds.

receiveUPS.txt -

Once the match is found in the text file, the shipping rate is then sent as a variable in the HTML URL. print "<script type = 'text/javascript'> location.href=\"receiveUPS.html?charge=$price\"</script>

The variable charge is then read by receiveUPS.html which calculates the total invoice cost with the new shipping rate included. In this example, the shipping rate of a 10 lbs package using UPS Ground is $11.


Working Example

The following is a working example of the UPS web service:


Request UPS shipping charges

Credit Card Validation

The following example is only a demo of a true credit card validation web service. This sample web service checks to make sure that the credit card number is 16 digits in length and also verifies that all Visa credit cards begin with with the number 4 (like in the real world).

Billing Information
First Name:
Last Name:
Billing Address:

Credit Card Information
Total Amount:
Credit Card Type:
Credit Card Number:

Web Service Methods

There are two main methodologies of accessing Web services: one is URI-based and the other uses Remote Procedure Calls (RPC). We will examine the URI-centric REST and then the SOAP-RPC methods. Uniform resource information (URI's) may be the familiar URL but could also be simply an abstract reference to resource information.

REST is a standard and an architectural style that uses URI's to access data resources. SOAP is a communication protocol, not a standard or style, that relays resource data requests and responses. Further information on REST and SOAP.


REST stands for REpresentational State Transfer. REST is an architectural style for network-based systems, as described by Dr. Roy Fielding in his disseration. He explains that REST "is intended to evoke an image of how a well-designed Web application behaves: a network of Web pages (a virtual state-machine), where the user progresses through an application by selecting links (state transitions), resulting in the next page (representing the next state of the application) being transferred to the user and rendered for their use."

REST Web services provides URIs to access resource data, commonly in the form of XML. Making use of HTTP as its communication protocol and XML resource data allows businesses to communicate the data on any given platform.

REST Example:

Acme, a ficticious shirt supplier, has some Web services that allows its clients to:
  • get a list of shirt syles
  • get detailed information about a particular shirt
  • submit a Purchase Order (PO)
Acme's Web service has a URL that will retrieve a list of shirt styles in XML format:
The URL request returns the following data:

<?xml version="1.0" encoding="iso-8859-1" ?>
<p:Shirts xmlns:p="http://www.acme-shirts.com"

    <Name>short sleeve crew</Name>
    <Name>long sleeve crew</Name>
        <Name>tank top</Name>


A link to the Web service URL makes available a shirt styles list resource. Note that how the Web service generates the parts list is completely transparent to the client. This XML data would then be displayed to the client user. The shirt styles resource also provides a URL that would retrieve further data on a particular style of shirt.This is a key feature of REST. The client transfers from one state to the next by examining and choosing from among the alternative URLs in the response document.

Logical vs. Physical URLs

A logical URL:
A physicalURL:

Using logical URLs saves the Web service developer from having to make several static pages. With a logical URL, the Web service would take the URL request, parse it to determine what is being requested, query the database,and generate the response document which is returned to the client. This would be much more efficient than, say, writing a HTML page for each shirt style.

Acme example continued ...

Acme also provides a Web service that allows clients to submit Purchase Orders (PO). The Web service makes available a URL to submit a PO. The client creates a PO instance document which conforms to the PO schema that Parts Depot has designed (and publicized in a WSDL document). The client submits PO.xml as the payload of an HTTP POST. The PO service responds to the HTTP POST with a URL to the submitted PO. Thus, the client can retrieve the PO any time thereafter. The PO has become a piece of information which is shared between the client and the server. The shared information (PO) is given an address (URL) by the server and is exposed as a Web service.

Using REST with PHP

To retrieve the XML data via REST (URL) in PHP, you will need to call built-in PHP functions that opens a file and stores XML into a variable. Look at the following code:


while (!feof ($xurl))

    $xml .= fgets($xurl, 4096);

fclose ($xurl);

fopen(*URL*, *read/write*) retrieves the file from the URL, the first argument of the function. The second argument refers to whether the file is read-only or not. "r" means the file will be read-only.

fgets(*resource handler*, *buffer size*) points at a line in the file. The first argument is the resource to be looked at, in this case it is the opened file. The second argument is a buffer size, and 4096 is large enough to work with.

fclose(*resource handler*) closes the opened file.

Once the XML stored in a variable, you will need to parse the XML into an array. PHP has built-in functions to do this. Look at the following code:

// Start the built-in XML parser

$parser = xml_parser_create(  );
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);

// Set tag names and values


// Close down XML parser


xml_parser_create() creates a new XML parser.

xml_parser_set_option() sets the options of the parser. XML_OPTION_CASE_FOLDING uppercases elements.

xml_parse_into_struct ( resource parser, data, array &values [, array &index]) actually parses the XML into an array.

xml_parser_free( closes the parser.

Now, the data for each element is stored into an array by it's element name. Refer to the PHP manual for more information on these functions.


SOAP stands for Simple Object Access Protocol. In Web applications, a request for an application comes from the client computer and is transmitted over the Internet to the server computer. There are many ways of doing this, but SOAP makes it easy by using XML and HTTP - which are already standard Web formats.

SOAP is a simple XML based protocol to let applications exchange information over HTTP. Simply stated, SOAP provides a way to access services, objects, and servers in a completely platform-independent manner. Using SOAP you can query, invoke, communicate with, and otherwise touch services provided on remote systems without regard to the remote system's location, operating system, or platform.

A SOAP transaction begins with an application making a call to a remote procedure. The SOAP client script then encodes the procedure request in XML and sends it over HTTP to a server script. The server parses the request and passes it to a local method, which returns a response. The response is encoded into XML by the server and returned as a response to the client, which parses the response and passes the result to the original function.

There are two main ways to create and send a soap request to a server:

  1. NuSoap (PHP based)
  2. XML Spy (graphical user interface)


There are several implementations of SOAP under PHP. The most popular used implementation is NuSOAP, an external PHP library downloadable at Consuming Web Services with PHP.


Let's take a Barnes & Noble Price Quote server. One of BN's SOAP server methods is getPrice. The method takes an ISBN as input and returns price data from Barnes & Noble. Here is the client script that calls the getPrice:


// include the SOAP classes

// define parameter array (ISBN number)
$param = array('isbn'=>'0385503954');

// define path to server application
$serverpath ='http://services.xmethods.net:80/soap/servlet/rpcrouter';

//define method namespace

// create client object
$client = new soapclient($serverpath);

// make the call
$price = $client->call('getPrice',$param,$namespace);

// otherwise output the result
print "The price of book number ". $param['isbn'] ." is $". $price;

// kill object

In the example, the PHP script first includes the NuSOAP class with the methods needed to access SOAP services. An array $params is created to store the input parameters for the BN's price method. Next, the URL of the server application is stored in the variable $serverpath and the namespace of the method is stored into the variable $namespace. It then creates an instance of a SOAP client called $client. The script then makes a call to BN's SOAP server via the call() method, passing the method name, parameters, and the namespace of the method as its arguments. NuSOAP parses the results in the SOAP response envelope into an array stores it into $price. The result is printed out and the client object is killed.

A Closer Look at the Transaction

An envelope defines the XML to be a SOAP message. In the body of a request envelope, the client makes a call to procedures and passes its arguments. Here is the example's SOAP request:



<ns1:getPrice xmlns:ns1="urn:xmethods-BNPriceCheck"

<isbn xsi:type="xsd:string">0385503954</isbn>




The SOAP request is calling a procedure getPrice and with the ISBN argument, 0385503954. The SOAP server receives the request, decodes the procedure calls and invokes the procedure. The server then packages the response into a SOAP envelope and sends it back to the client.

Here is the example's SOAP response:



<ns1:getPriceResponse xmlns:ns1="urn:xmethods-BNPriceCheck"

<return xsi:type="xsd:float">18.2</return>




This SOAP envelope sends the client the getPriceResponse called return with the value of 26.

Applications written for different platforms can "speak" SOAP using HTTP, so they can communicate with each other using data. Platform differneces in native languages are ignored because of SOAP.


Similar to NuSoap, XML Spy also involves manipulating soap envelopes. However, XML Spy is a smart editing-tool that includes a graphical user interface for making eXtensible Markup Language (XML) solutions easier.

It claims to be an XML development environment to support the designing and editing of XML technologies; including XML editing and validation, Schema and Dtd design, and XSL transformation. XML Spy is the industry standard XML Development Environment for building software applications based on XML technologies.

What you'll learn from the following exercises:

Thanks to Jason Lien!

Exercise 1: Barnes and Noble Price Quote

This web service will return the price of a book given the ISBN at Barnes and Noble.

Creating a new SOAP request:

1. Open XML Spy 2004 (Enterprise Edition)

2. Select the menu option Soap | Create new SOAP request.

This opens a dialog box where you have to enter the local path or URL of a WSDL file describing the web service. Opening Soap Request

3. Click OK to confirm the selection and connect to the server. This opens a dialog box from which you select a specific SOAP operation.

Selecting Soap Methods

4. Click the getPrice (string isbn) entry, and confirm with OK. This creates an Untitled.xml document in XMLSPY 2004 containing the SOAP request data.

Soap Document

One of the features of XML Spy is the ability to view the Soap Document in "Grid" view which separates each tag into its own grid. Try switching over to "Text" view to see the tags. By comparison, entering in data for this soap request is more user-friendly in "Grid" view.

5. Click one of the fields to deselect the table highlighting. Before the request can be sent, we have to specify the ISBN to return its book price.

6. Click the text field, and enter 0439139597.

Entering in ISBN

Now that we have defined the Soap request document, the data needs to be returned back to the server.

Sending a Soap Request:

1. While the SOAP request document is active, select the menu option Soap | Send request to server.

After a few seconds, a new XML document is automatically created, containing the SOAP Response from the respective server. In this example, the price of the ISBN we entered earlier is displayed in the new document.

Soap Response

In this example, the price of a book with an ISBN of 0439139597 is $18.16.

Question 1:
Now that you are familiar with soap requests and how it works with XML Spy, what is the price of the XML Spy Reference Manual at Barnes and Noble -- with ISBN of 0595219020?.

Exercise 2: Easter Date Calculator

This web service calculates the date of Easter when given a year.

The URL for this web service is: http://www.stgregorioschurchdc.org/wsdl/Calendar.wsdl

Question 3:
What date does Easter fall on in the year 2010?

For more Soap web services, visit www.xmethods.com

XML Parsing

While NuSoap and XML Spy both use SOAP to transport data, XML data can be sent through HTTP using XML parsing as well.

XML allows document authors to create their own tags, immediately making it more powerful and flexible than HTML. Once a file has been created, it needs to be converted from pure data into something more readable.

However, most browsers do not come with an XML parser or an XSL processor. The latest versions of Internet Explorer and Netscape Gecko do support XML, but older versions do not. Using PHP is one way to read XML data source to generate HTML for these older browsers.

The following script by Brian Ellison shows how to use PHP to read an XML data file and create an HTML table with the XML data. His method is general, so it will probably work for most XML files.

Reading XML with PHP scripts

PHP uses native XML parsing functions for getting data from XML documents. An XML document is read in from beginning to end, setting off an event whenever a start tag, end tag, or block of character data is encountered. The data contained in the tags is parsed then stored in an array which may be used by your PHP script for output.

The Code to Parse XML Using PHP

This example (with explanations of the code in red) demonstrates how to get the XML data from the following page :
http://www.classanytime.com/mis373/db/inventory.xml. The code can be modified to get data from most XML pages.


// The variables in xItem are the data you want to extract from the XML page.
In this case we are parsing the ID, ItemName, Description, Price, and Quantity

class xItem {
  var $xID;
  var $xItemName;
  var $xDescription;
  var $xPrice;
  var $xQuantity;

// Declare variables to hold XML data

$arItems = array();
$itemCount = 0;

// URL of XML page to find data 

$uFile = "http://www.classanytime.com/mis373/db/inventory.xml";

// startELement function gets the first tag

function startElement($parser, $name, $attrs) {
  global $curTag;
  $curTag .= "^$name";

// endElement gets the closing tag

function endElement($parser, $name) {
  global $curTag;
  $caret_pos = strrpos($curTag,'^');
  $curTag = substr($curTag,0,$caret_pos);

// get the data in between the open and closing XML tags

function characterData($parser, $data) {
  global $curTag;

  // Reference the data in the XML document to extract.

  global $arItems, $itemCount;
  $itemTitleKey = "^INVENTORY^ITEM^ID";
  $itemMainPriceKey = "^INVENTORY^ITEM^PRICE";
  $itemMainQuantityKey = "^INVENTORY^ITEM^QUANTITY";
  $itemSupplier = "^INVENTORY^ITEM^SUPPLIER";

  // When going through all the items, be sure to go in the order
  // that the data comes in the XML document.  For example, in our
  // XML document the ID comes, first, then the Itemname, then the
  // description, and so on.  It is important to go in order because
  // the parser goes from top to bottom.

  if ($curTag == $itemTitleKey) {
    // make new xItem
    $arItems[$itemCount] = new xItem();

    // set new item object's properties
    $arItems[$itemCount]->xID = $data;
  elseif ($curTag == $itemLinkKey) {
    $arItems[$itemCount]->xItemName = $data;
  elseif ($curTag == $itemDescKey) {
      $arItems[$itemCount]->xDescription = $data;
  elseif ($curTag == $itemMainPriceKey) {
      $arItems[$itemCount]->xPrice = $data;
  elseif ($curTag == $itemMainQuantityKey) {
        $arItems[$itemCount]->xQuantity = $data;
  elseif ($curTag == $itemSupplier) {
        $arItems[$itemCount]->xSupplier = $data;
    // increment item counter

// This PHP parser code is uses the functions above 
and stores the XML data into arrays created earlier.
$xml_parser = xml_parser_create(); xml_set_element_handler($xml_parser, "startElement", "endElement"); xml_set_character_data_handler($xml_parser, "characterData"); if (!($fp = fopen($uFile,"r"))) { die ("could not open RSS for input"); } while ($data = fread($fp, 4096)) { if (!xml_parse($xml_parser, $data, feof($fp))) { die(sprintf("XML error: %s at line %d", xml_error_string(xml_get_error_code($xml_parser)), xml_get_current_line_number($xml_parser))); } } xml_parser_free($xml_parser); // Output the data ?> <html> <head> <title>XML report of inventory data</title> </head> <body> <table cellpadding="3" cellspacing="0" border="1" style="border:1px solid silver;"> <tr> <th scope="col">Number</th> <th scope="col">ID</th> <th scope="col">Name</th> <th scope="col">Description</th> <th scope="col">Price</th> <th scope="col">Quantity</th> <th scope="col">Supplier</th> </tr> <?php // Loop through the array to extract the parsed data for ($i=0;$i<count($arItems);$i++) { $txItem = $arItems[$i]; ?> <tr> <td scope="row"<?php echo $i; ?></td> <td<?php echo($txItem->xID); ?></td> <td<?php echo($txItem->xItemName); ?></td> <td<?php echo($txItem->xDescription); ?></td> <td<?php echo($txItem->xPrice); ?></td> <td<?php echo($txItem->xQuantity); ?></td> <td<?php echo($txItem->xSupplier); ?></td> </tr> <?php } ?> </table> </body> </html>


See what the php code will output.

More Information

The following links have further information about the PHP XML built in parser.

Web Service Exercises

The exercise deal with making calls to a web service and presenting the retrieved data on a page. You will be using PHP to manage the web service calls. Create a page that includes an Amazon Top 10 Bestsellers sidebar and a Web search form as described below.

Exercise 1: Amazon Bestsellers (REST)

This first component will take advantage of Amazon's Web Services. Using Amazon's extensive API, you will use REST calls to retrieve XML data to be used on your page. Somewhere on the front page of your site, create a sidebar that displays Amazon.com's top 10 bestsellers for a subject of your interest. Here is a list of possible searches that Amazon makes available:

Search Description
Keyword Searches for a user-specified keyword
Browse Node Searches for a user-specified browse node (category)
Author Searches for a user-specified author
Artist/Musician Searches for a user-specified artist or musician
Actor/Actress Searches for a user-specified actor/actress
Director Searches for a user-specified director
Manufacturer Searches for a user-specified manufacturer
Power Searches for a user-specified power search

Querying Amazon Web Service will return the results in XML, which will need to be parsed into a list.

  • Relevant element names to be used are: 'Asin', 'ProductName', 'Artist' or 'Authors', and 'OurPrice'
  • Your PHP script will build a list to display the results
  • Place list somewhere right or left of your page
  • Each item listed should be linked to Amazon page via the returned 'Asin' in the form of http://www.amazon.com/o/ASIN/[Asin]

To access Amazon's Web Services, you must use a security token. You may use this token: D3JONB1AX0R25J. Tokens are free and available from Amazon.

Exercise 2: Google Search (SOAP)

Here, you will be taking advantage of Google's web search API. On your page, you will have a search box that will make SOAP calls to Google's web services. To handle the SOAP calls using PHP, you will need to use the NuSOAP library.

Search box
  • The SOAP search request parameters can be found here.
  • Google's web service search operation is named doGoogleSearch.
  • The namespace for Google's doGoogleSearch is called urn:GoogleSearch.
  • Google also requires a security token. You may use nU6hkPZQFHJTNzfhCkYADo9JfcY0i2sE. They are free and available here.
  • Relevant element names to be used are:
    • 'resultElements' - array of results
    • 'title' - title of result
    • 'URL' - the URL of the site
    • 'snippet' - a small description of the result
  • Print out just the top 10 results into a list with snippet on a separate page titled eprojectx-google.php
  • Each result should be linked to the respective sites
  • Search box must be able to accept multiple terms and specific phrases
  • Add a link back to the main page

Search Results for "johnny cash" in 2004

  1. johnnycash.com
    Enter JohnnyCash.com.

  2. Johnny CashCareer
    ... and Johnny CashSings Ballads Of The True West (1965). People forget just
    how hot Johnny Cash was, when his sales career was at its zenith. ...

  3. johnnycash.com
    ... painting. Johnny Cash has been a household name for more than most
    people can remember, and his career spanned nearly five decades. ...

  4. CNN.com - 'Man in Black' Johnny Cash dead at 71 - Sep. 12, 2003
    ... Man in Black' Johnny Cash dead at 71. ... The Johnny Cash video for 'Hurt' covers
    a Nine Inch Nails song and was nominated for several 2003 MTV video awards. ...

  5. Johnny Cash/ Man In Black
    ... someone -. 1932-2003. Established February 24, 1998. ash Johnny Cash
    Johnny Cash Johnny Cash Johnny Best viewed in 1024x768. The above ...

  6. Johnny Cash

  7. Johnny Cash - The Man in Black
    Johnny Cash lyrics, pictures, mp3, audio files, sound samples, biography,
    facts, address, and concert informatio. I'll fly a starship ...

  8. BBC NEWS | Entertainment | Music | Country legend Cash dies
    Singer Johnny Cash, one of country music's most iconic stars, dies in the US aged
    71. ... CASH'S LIFE IN PICTURES. Images spanning the career of Johnny Cash. ...

  9. Johnny Cash Lyrics
    Johnny Cash Classic Lyrics. I plan on adding more lyrics here. Please stop back.
    If you are looking for chords, TRY HERE. Written by JR Cash. Big River. ...

  10. Johnny Cash/ Man In Black
    ... someone -. 1932-2003. Established February 24, 1998. ash Johnny Cash
    Johnny Cash Johnny Cash Johnny Best viewed in 1024x768. The above ...