Using XML technology to construct remote services in PHP (1)_PHP tutorial

The future web will be a service-centered web, and the xml_rpc standard makes it very simple to write and apply services. This article introduces the xml_rpc standard and its PHP implementation, and demonstrates how to develop xml_rpc services and client programs in PHP through examples.

1. Serviced web

From the simple methods adopted by content providers to the future ideas of uddi (universal description, discovery and integration), the industry has already seen a large number of Notes and comments about the "serviced web". In the early stages of the web, it was just a collection and distribution center for documents, providing only browsable information. With the development of the web, running services on the web is becoming more and more attractive. In the future, the web will become a carrier for enterprises to provide convenient services to customers and other enterprises. The collaboration between b2b and b2c models can be regarded as a service web.

A very important question is, what services can be provided on the web? The web can provide many services, some of which are already in use now, and some of which will appear in the near future. To illustrate the problem, here is a small list of services that can be provided through the web:

◆ Topic-oriented vertical search engine.
◆Knowledge base for users to find information.
◆Expert system where users can ask questions.
◆Banking services.
◆News and information publishing services.
◆Digital payment related services.
◆Graphics processing services.
◆Health and wellness services.

So, what is the correct way for enterprises and organizations to provide services through the web? This is a very important question. Today, some services provide html interfaces, and they provide services in the form of documents, but what is hidden behind the service interface? Web browsers are not alone in the race to dominate the web. Mobile phones, handheld devices, and devices like microwave ovens all want to access the web, query databases, transform data, extract information, and more. To achieve a truly serviced web, there should be another layer below the presentation layer (html).

2. xml_rpc standard

xml may be the most important standard in the past 10 years. The xml vocabulary provides the cornerstone for enterprises to construct service environments. To build a serviced web, it is necessary to learn the xml_rpc standard, not only because xml_rpc is useful for putting services on the web, but also because xml_rpc is an already established standard that is easy to adopt. For B2B services, the standards for providing services are extremely important. Companies that jointly follow the standards can achieve rapid growth by utilizing the services provided by other companies. It is impossible to imagine that a truly serviced web can be built on various private service standards. Services must have a standard that can be followed.

xml_rpc is a standard for Internet distributed processing. RPC is the abbreviation of remote procedure call. It is a remote calling mechanism used to call procedures that may reside on other machines and may be written in other languages. Remote procedure calls are an important pillar of distributed computing. For example, in a distributed computing environment, we can find and exploit processes that perform addition and subtraction operations running on other machines. The process that performs the addition operation may be written in APL and runs on the rs6000 machine. The process that performs the subtraction operation Probably written in C and running on Unix. Other developers who want to use such distributed calculators can also use them, or they can choose another better calculator.

In rpc, procedure is the most important component, and the server provides the process for the client to call. Procedures can receive parameters and return results. xml_rpc uses http as the protocol carrier and implements the rpc mechanism through the xml vocabulary for sending and receiving data. The xml_rpc server receives the xml_rpc request and returns the xml_rpc response. The xml_rpc client program sends the xml_rpc request and receives the xml_rpc response. Servers and clients must handle responses and requests in accordance with the requirements of the xml_rpc standard.

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