Web Service

Introduction

Web Service is a standard way of interoperating between different software applications running on a variety of platforms and/or frameworks. It allows for seamless communication and data exchange between disparate systems.

Types of Web Services

• SOAP: Stands for Simple Object Access Protocol. It is a protocol for exchanging structured information in the implementation of web services in computer networks.
• RPC: Remote Procedure Call is the most common messaging pattern used in web services where a client invokes a procedure on a remote server.
• REST: Representational State Transfer is an architectural style that uses a stateless, client-server communication protocol. Resources are identified by global identifiers (URIs) and accessed via HTTP methods.

RESTful services do not have a WSDL (Web Services Description Language) and are commonly used by websites that provide RSS and RDF feeds. Services like Delicious offer XML data that can be consumed by clients using SimpleXML.

Key Terminologies

• WSDL: Web Services Description Language is an XML format for describing network services as a set of endpoints operating on messages.
• UDDI: Universal Description Discovery and Integration is a directory service where web services can be registered and discovered.

PHP and Web Services

In PHP, NuSOAP is a popular SOAP library used to create and consume SOAP-based web services. PHP provides built-in tools like SoapServer and SoapClient for implementing web services.

Server-side Implementation

// Define the SOAP server
$options = array('uri' => 'http://example.org/soap/server/');
$server = new SoapServer(NULL, $options);
$server->setClass('MySoapServer');
$server->handle();

Client-side Implementation

try {
    $options = array(
        'location' => 'http://example.org/soap/server/server.php',
        'uri' => 'http://example.org/soap/server/',
        'trace' => 1
    );
    $client = new SoapClient(NULL, $options);
    
    // Call the method on the server
    $results = $client->method(param);
    
    // Debugging information
    echo $client->__getLastRequestHeaders(); // Display request headers
    echo $client->__getLastRequest(); // Display request XML body
} catch (SoapFault $e) {
    echo $e->getMessage();
}