Continuous Learning

The foundation of Wordpress API is built on XMLRPC, and hence if you want to know how the API works then you need to know XMLRPC.

XMLRPC Specification

The authoritative source about XMLRPC is its spec, which includes the following information:

1. Sample request & response
2. Method name
3. XML representation of scalar data (boolean, integer, double, date, string, and base64)
4. XML representation of complex data (array and struct)
5. Failure response

You might find the spec itself is a bit sparse (which is a prevalent feature in the whole xmlrpc.com), and might want to have some tutorials and samples to go along with the information. Furthermore, who wants to manually construct XML these days?? We want a library to do the work!

PHP Implementations of XMLRPC

It turns out that many people have answered the call - I found that at least 5 major branches of XMLRPC libraries in PHP (there are probably more, but I can’t boil the ocean ;P):

• PHP itself has included an experimental xmlrpc functionality, which can be turned on/off
• The PHP experimental xmlrpc functionality is based on eOpinion’s library
• PEAR also has a library for XMLPRC called PEAR::XML_RPC
• PEAR’s library is based on Edi Dumbill (Useful Inc)’s XML-RPC package
• Lastly but not least, Incutio has a very easy to use XML-RPC package (this is the package used by WP)

How should one go about choosing the right package to use? Below is my quick checklist for decision points:

• Is the library stable?
• Will the library be supported?
• Will the library be available?
• Will the library require additional effort to get setup (e.g. require compilation process)?

And how the libraries stack up:

Conclusion

While the pure library XML-RPC package such as Useful Inc’s or Incutio’s do not necessarily offer speed, IMHO they are easier to include for distribution, better documentation, and possibly active support.

When comparing the two package, what I found is that:

• Useful Inc’s has more active development and better documentations
• But Incutio’s is easier to use, and is used in WP

What really sold me with Incutio’s package is that by default it assumes that you shouldn’t have to even think in XML at all - it helps you handle as much of conversion from XML to PHP objects as possible, where Useful Inc’s version still requires you to explicitly control the conversion (it does have helper functions that will simplify the process). Incutio’s abstraction will help speed up the development of a WP XMLRPC client.

We will talk about the various API for WP next.