PHP Manual: Working with Data Structures

Working with Data Structures

SCA components can pass and return the four PHP scalar types boolean, integer, float and string, but to pass or return data structures, SCA components use Service Data Objects (SDOs). SDOs are described in much more detail in the SDO pages of this manual. Readers familiar with SDOs will know that they are suitable for representing the sort of structured and semi-structured data that is frequently modeled in XML, and that they serialize very naturally for passing between remote components, or in Web services. SDOs are presently the only supported way to pass and return data structures. It is not possible to pass or return PHP objects, or PHP arrays.

The SCA runtime always assures data is passed by-value, even for local calls. To do this, the SCA runtime copies any SDOs in the parameter list before passing them on, just as it does for scalar types.

How data structures are defined to SCA components

Currently the only mechanism for specifying the location of a data structure definition is by specifying the types in an XML schema file. However, in the future it may be possible to define types in other ways, such as based on PHP classes or interfaces, or based on definitions expressed as associative arrays.

To illustrate the use of SDOs we introduce a new component. The PortfolioMangement service below returns an SDO representing a stock portfolio for a given customer.

Example #1 A Component that uses Data Structures


<?php

include "SCA/SCA.php";

/**
 * Manage the portfolio for a customer.
 *
 * @service
 * @binding.soap
 *
 * @types http://www.example.org/Portfolio PortfolioTypes.xsd
 *
 */
class PortfolioManagement {

    /**
     * Get the stock portfolio for a given customer.
     *
     * @param integer $customer_id The id for the customer
     * @return Portfolio http://www.example.org/Portfolio The stock portfolio (symbols and quantities)
     */
    function getPortfolio($customer_id) {
        // Pretend we just got this from a database
        $portfolio = SCA::createDataObject('http://www.example.org/Portfolio', 'Portfolio');
        $holding = $portfolio->createDataObject('holding');
        $holding->ticker = 'AAPL';
        $holding->number = 100.5;
        $holding = $portfolio->createDataObject('holding');
        $holding->ticker = 'INTL';
        $holding->number = 100.5;
        $holding = $portfolio->createDataObject('holding');
        $holding->ticker = 'IBM';
        $holding->number = 100.5;
        return $portfolio;
    }

}
?>

The @types annotation:


<?php
@types http://www.example.org/Portfolio PortfolioTypes.xsd
?>

indicates that types in the namespace http://www.example.org/Portfolio will be found in the schema file located by the URI PortfolioTypes.xsd. The generated WSDL would reproduce this information with an import statement as follows:

<xs:import schemaLocation="PortfolioTypes.xsd"
                      namespace="http://www.example.org/Portfolio"/>

so the URI, absolute or relative, must be one that can be resolved when included in the schemaLocation attribute.

Creating SDOs

Readers familiar with SDOs will know that they are always created according to a description of the permitted structure (sometimes referred to as the 'schema' or 'model') and that, rather than creating them directly using 'new', some form of data factory is needed. Often, an existing data object can be used as the data factory, but sometimes, and especially in order to get the first data object, something else must act as the data factory.

In SCA, either the SCA runtime class or the proxies for services, whether local or remote, can act as the data factories for SDOs. The choice of which to use, and when, is described in the next two sections.

We switch to a new example in order to illustrate the creation of SDOs, both to pass to a service, and to be returned from a service.

Creating an SDO to pass to a service

A caller of a service which requires a data structure to be passed in to it uses the proxy to the service as the data factory for the corresponding SDOs. For example, suppose a component makes use of a proxy for a service provided by a local AddressBook component.


<?php
/**
 * @reference
 * @binding.local AddressBook.php
 */
$address_book;
?>

The AddressBook component that it wishes to call is defined as follows:


<?php
/**
* @service
* @binding.soap
* @types http://addressbook ../AddressBook/AddressBook.xsd
*/
class AddressBook {

    /**
     * @param personType $person http://addressbook (a person object)
     * @return addressType http://addressbook (the address object for the person object)
     */
    function lookupAddress($person)  {
        ...
    }
}
?>

The AddressBook component provides a service method called lookupAddress which uses types from the http://addressbook namespace. The lookupAddress method takes a personType data structure and returns an addressType. Both types are defined in the schema file addressbook.xsd.

Once the component that wishes to use the AddressBook component has been constructed, so that the $address_book instance variable contains a proxy for the service, the calling component can use the proxy in $address_book to create the person SDO, as shown below:


<?php
$william_shakespeare        = $address_book->createDataObject('http://addressbook','personType');
$william_shakespeare ->name = "William Shakespeare";
$address                    = $address_book->lookupAddress($william_shakespeare);
?>

Note, the use of the proxy as the means to create the SDO is not limited to SCA components. If a service is being called from a general PHP script, and the proxy was obtained with getService then the same approach is used.


<?php
$address_book = SCA::getService('AddressBook.php');
$william_shakespeare = $address_book->createDataObject('http://addressbook','personType');
?>

Creating an SDO to return from a component

A component that needs to create a data object for return to a caller will not have a proxy to use as a data object, In this case it uses the createDataObject static method on SCA.php. Hence if the AddressBook component described above needed to create an object of type addressType within the namespace http://addressbook, it might do so as follows:


<?php
$address = SCA::createDataObject('http://addressbook','addressType');
?>