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Introduction to Web services with PHP5 SOAP

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Introduction to Web services with PHP5 SOAP Powered By Docstoc
					?Note that both Googles service and PEAR SOAP are technically still in beta, so you
might encounter the odd bug from time to time. There are other SOAP client libraries
available, including the PHP5 SOAP extension and NuSOAP, and while
implementation details are different the basic theory is the same as presented here.

Setting up the PEAR SOAP module

Before we can start using SOAP, we had better make sure both PEAR itself and the
SOAP module are available. The PEAR package manager is installed by default with
PHP 4.3.0 and later, but if you are using an earlier version or it is missing on your
system check out the PEAR manual for instructions.

Once you have the package manager installed, you will need to download the SOAP
package. On most systems, you can just enter pear install SOAP into a console
window. At least, thats the theory. Unless there is a stable release of SOAP available,
you will get the message No release with state equal to stable found for SOAP. Try
pear install SOAP beta to get the most current version of the package at the time of
writing, even though it is in beta, or tell PEAR to accept beta versions without
complaint by typing pear config set preferred state beta.

You may also get one or more messages starting with requires package, followed by
Dependencies failed. In this case, try the pear install command again but add the
dependencies on the command line. For example, if PEAR complained that the Net
DIME package is missing, try using pear install Net DIME SOAP instead.

Getting a license key

Once you have installed the SOAP module, the next step is to download the Google
Web APIs developers kit and register to get a license key. This key allows you to
make up to 1000 SOAP queries a day free of charge. Visit Google Web APIs http
/pagead/show_ads.js">

Decoding the WSDL file

In the developers kit main directory you will find a WSDL file called
GoogleSearch.wsdl, which you can open in a text editor or XML browser. This file
defines exactly what services we can call using SOAP, though the Google
documentation is probably easier to read.

However, we can also see what the SOAP module makes of this file. Create a new
PHP page and enter the following.


require once SOAP Client.php
wsdl new SOAP WSDL GoogleSearch.wsdl.
header Content Type text plain
echowsdl generateProxyCode.




Place it somewhere on your server along with GoogleSearch.wsdl and access it
through your web browser. Assuming everything is working right, you should get a lot
of PHP code output. This code is the result of the SOAP WSDL client class parsing
the WSDL file and converting it into PHP functions. This tells us what functions we
can call in a rather more readable form than the WSDL document, and is handy
particularly if you are using a poorly documented WSDL service.

So how does the code work Let s go through it step by step.

1. First, we load the SOAP client file. If this gives an error, it probably means SOAP
isnt installed properly and you should read the instructions above or the PEAR
manual.

2. We then create an instance of the SOAP WSDL class, based on the
GoogleSearch.wsdl file. This is one of the main classes we are going to use
throughout this tutorial it parses the WSDL file and represents it as PHP.

3. Finally, we output the proxy code as plain text. As you can see from the output, in
SOAP the proxy is a class that represents the WSDL calls available as PHP functions.

Spell checking with Google

If you ve been using Google for a while and type as erratically as me, you have
probably noticed the Did you mean line that appears if you misspell a word in a
search. Thanks to the Google web service, we can add this spelling checker to our
PHP applications though to be honest, it would probably be better to use pspell in an
actual application. Enter the following code, with your own license key as the first
string.




Simple, isn t it The first line is trivial and the next two are the same as the previous
example. The fourth line creates the proxy object based on the code we looked at
earlier, so we can make SOAP requests by calling its methods. Finally, we call
doSpellingSuggestion and output the result. Access this page in your web browser,
and you should see the word dictionary on its own.

You might see Object instead, in which case SOAP has encountered a problem and
returned a SOAP Fault object. We will look into dealing with these faults sometime in
the future, but for now check if you have entered your license key correctly and not
managed to exhaust your 1000 query per day limit .

				
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