SOAP

SOAP is an acronym for Simple Object Access Protocol. It is a messaging protocol to exchange structure data, based on XML.

PHP supports SOAP with a native extension called ext/soap.

<?php

// Example from the soap documentation in PHP

function Add($x,$y) {
  return $x+$y;
}

class LocalSoapClient extends SoapClient {

  function __construct($wsdl, $options) {
    parent::__construct($wsdl, $options);
    $this->server = new SoapServer($wsdl, $options);
    $this->server->addFunction('Add');
  }

  function __doRequest($request, $location, $action, $version, $one_way = 0) {
    ob_start();
    $this->server->handle($request);
    $response = ob_get_contents();
    ob_end_clean();
    return $response;
  }

}

$x = new LocalSoapClient(NULL,array('location'=>'test://',
                                   'uri'=>'http://testuri.org'));
var_dump($x->Add(3,4));
?>

Documentation