Category: REST

Packt Publishing kindly sent me a copy of RESTful PHP Web Services by Samisa Abeysinghe to review. The book’s cover claims that it will help you “Learn the basic architectural concepts and steps through examples of consuming and creating RESTful web services in PHP”. The book succeeds in providing simple steps and examples of creating and consuming web services, but falls short on REST architectural concepts and design principles.

The book starts with a very brief introduction to the principles of REST, and rapidly moves on to a discussion of PHP tools frameworks. The introduction misses some important REST / RESTful web service concepts such as hypermedia, application vs resource state and the relevance of utilising HTTP headers and status codes. Some of the information in the introduction is confusing. For example, on page 12, it says “Resources can have multiple representations that reflect different application states”. This does sound a little odd – resources can have multiple representations, for example, for different requested content types. Representations should reflect resource state, not application state. Also, the coverage of HTTP verbs is misleading, especially when POST and PUT are discussed.

The next couple of chapters discuss PHP support for HTTP, using libraries such as CURL, and XML parsing strategies. The author chooses realistic examples for code samples, such as Flickr and Yahoo Maps clients. The last example given is quite cool – using earthquake latitudes and longitudes from an Australian government site to plot points on Yahoo maps. The example code is generally simple and easy to follow. However, it would have been nice to see some sort of separation between view and data access logic.

The following chapter is a worked example of building RESTful services for a library lending books. It is a good example, and becomes the basis for most future chapters. The resource design and URLs are reasonable, although it may have been nice to have “loans” as resources in their own right. Using links between resources, rather than just relying on known URLs would also benefit the design.

Later chapters cover alternative frameworks such as Zend and WSO2 using the library lending system as an example for code samples. These chapters are useful as they give an idea how the frameworks look when put in practice. It does look as though PHP and frameworks still have significant limitations around routing flexibility from the examples (eg, the .php extension seems to mandatory in URLs). There is also a chapter on debugging with tips around tools and troubleshooting XML parsing issues.

The writing style is generally clear and easy to read. There are occasionally some odd turns of phrase, such as on page 10: “AJAX makes Web applications to become more interactive, faster, and more user-friendly”.

Overall, I would recommend this book to people wanting to write simple URI template based web services or clients in PHP, and also to people interested in getting an overview of libraries and frameworks currently available in the PHP ecosystem. To gain an understanding of the REST architectural constraints and designing good RESTful systems, I would recommend RESTful Web Services, and if you wanted to take it further, digging into Roy Fielding’s thesis and the HTTP 1.1 Spec.