Integrating PHP CMS Systems with Web Services

There are many PHP CMS Frameworks which provide the capability to easily handle a quality web site which needs daily maintenance. Drupal , Joomla are two such CMS frameworks. These are grate tools for building web sites and managing content. How ever they are functioning in isolation.  When a site grows big, these systems happen to have a lot of valuable data that needs to be integrated with other enterprise systems in order to add business value.

For example consider an enterprise which has build its main web site using one of these tools and has many registered users to this site. Now the enterprise wants to incorporate these users to another application which the enterprise is running, because it wants to provide single sign on capability without having make the users go through another tiresome registration workflow. Also think a scenario where this other system is running on java or .net.

One obvious solution would be to share the database used by the CMS framework for the other application. But such a thing would add many complexities and would require one of the systems to be changed which is not doable in many situations. Now if the other system provides some programmable API or a web services API, then there is an elegant way to solve this integration problem.

With the availability of WSF/PHP  Data Services solution, now you have an easy way to overcome such problems. You can exposed data manipulation operations of the CMS database as web services using WSF/PHP Data Services. Now the two systems can talk to each other using their respective web services and clients, and you have a beautifully integrated solution. 

Debugging PHP Web Services

One of the difficulties of doing distributed computing, is the difficulty of debugging when things are not going well. It is no exception for Web Services. Since messages are exchanged between services, clients, we have to have some mechanisms  to capture messages, view the soap messages exchanged, some known error messages etc.

Capturing Messages

One of the most well known technique in debugging web services calls is to  some tcp message capture tool to capture the messages exchanged. There are few such good tools for this task.

1. TCPMON tool from apache

             This is a very simple and easy to use tool which has very wide adoption and is quite popular among developers. You can download this tool from apache tcpmon site. 

2. SOAP UI

            This is another popular tool for debugging and developing SOAP based applications. This tool is able to generate request SOAP message for a given WSDL where you fill out the values and send a valid soap request and response. This is a very useful tool to get started with Web Services. You can download soap UI from soapui.org

3.   Ethereal

         This is another tool that is quite useful is capturing and analyzing messages. http://thud.ethereal.com/

Using debugging functions from framework

you can you framework provided functions for debugging. For example WSF/PHP provides two functions getLastRequest() and getLastResponse() on the WSClient class which returns the exchanged request and response messages. Also it provides functions to obtains the returned HTTP headers. Using these, you can also do some debugging.

Logging

Logging is another useful techniques to idenfity possible problems. You can look as the wsf_php_client.log and wsf_php_server.log files and get an idea of what went wrong. If you are not able to trace what's wrong using the logs , you can post your problem with the appropriate log messages to the forum  and get support.

Using Known Error Messages

Another useful technique is to go through the known set of error messages to locate what went wrong. In WSF/PHP, here are some of the error messages you can get.

Implementing Rest Service and Client with WSF/PHP

WSO2 WSF/PHP 2.0.0 has support for HTTP verbs GET,POST,DELETE and PUT in its REST support alone with the ability to support custom URL mappings. Lets have a look at the WSF/PHP REST API and how to implement a simple client and service.

Usually, a REST system is build around CRUD ( Create, Read, Update, Delete ) model.

An HTTP POST Request is a creation of a resource. Similarly a GET request is reading, PUT request is updating and DELETE request is deleting.

You can find details of a design of a complex REST system here.

Implementing a PHP Web Service that can expose its operations as REST operations.

For exposing operations as REST operations, WSService constructor provides the option RESTMapping to specify each operation with its corresponding HTTP method and Custom URL that is mapped to the operation.

Lets consider an example.  Consider we have an operations createUserAccount, updateUserAccount, deleteUserAccount, and readUserAccount as the operations of a simple service called ManageUserAccounts.php

Then out operations map would be like

   1: $operations = array("createUserAccount" => "createAccount",

   2:                "updateUserAccount"=>"updateAccount",

   3:                 "deleteUserAccount"=>"deleteAccount",

   4:             "readUserAccount"=>"getAccount");

Here, the actual php functions implementing the business logic are  createAccount, updateAccount, deleteAccount and getAccount.

Now we can map these operations to an HTTP method and a custom URL, so that we can execute these same operations without having to use SOAP. 

   1: $restmap = array ("createUserAccount"=> array("HTTPMethod"=>"POST","RESTLocation"=> "users"),

   2:           "updateUserAccount"=> array("HTTPMethod"=>"PUT","RESTLocation"=> "users"),

   3:           "deleteUserAccount"=> array("HTTPMethod"=>"DELETE","RESTLocation"=> "users"),

   4:           "readUserAccount"=> array("HTTPMethod"=>"GET","RESTLocation"=> "users"));

Note how HTTPMethod is used to specify the HTTP Method that will be used to invoke each operation. For example, we will be using POST method to  invoke "createUserAccount" operation. 

RESTLocation option is used to specify a portion of a URL which will makeup the final URL of the operation. For example, if our service URL  is "http://localhost/samples/ManageUserAcconts.php" then, since we have set "users" as our RESTLocation, the final URL that will make the endpoint would be "http://localhost/samples/ManageUserAcconts.php/users". Note how I have used the same RESTLocation for all four operations. WSF/PHP is able to identify the correct operation using the HTTPMethod when the URL is the same.

Implementing the client

WSClient class which is the Client API in WSF/PHP API enables you to make use of  HTTP verbs POST,GET,DELETE and PUT when making a REST style operation invocation. 

First you need to know the REST endpoint where the resource is located. Consider we are invoking the "readUserAccount'' function defined in above service. Then our endpoint URL is  "http://localhost/samples/ManageUserAcconts.php/users" and HTTPMethod is GET. You can do this request using WSClient as well as using the Web Browser.

   1:     $client = new WSClient( array("to" => "http://localhost/samples/ManageUserAccounts.php/users",

   2:                                   "useSOAP" => FALSE,

   3:                                   "HTTPMethod" => "GET"));

   4:  

   5:     /** Request Payload String is the XML String send as argument to the operation, 

   6:         In this case, it will be send in query string */

   7:                 

   8:     $responseMessage = $client->request($requestPayloadString);

Similarly you can invoke other operations as well.  I will discuss more details in another blog post.