Some notes on Amazon, Tarzan, and Yii

Today Amazon announced yet another new name for its excellent product feed API: Product Advertising API. It was formerly called the Amazon Associates Web Service, and it provides access to Amazon’s vast database of product offers and related content such as user reviews. It has been around since 2004 so it’s certainly not a new service, but I recently decided it was time I tried it out.

Choosing an API implementation
Implementing the API manually wouldn’t be too hard, but I figured someone would have done it for me already. Surprisingly, I did not find anything for Python that seemed mature or up-to-date. PyAWS was last touched in 2007, and pyecs only implements a subset of the API operations.

Although I’m sure something could be built on pyecs or PyAWS, I found that both PHP and Ruby had more mature packages available, in the shape of Tarzan and ruby-aws. Having also wanted to look into PHP web frameworks for a while, I decided this was a good opportunity so I went with Tarzan.

Choosing a PHP web framework
There’s a gazillion PHP frameworks out there, and most of them seem to have their fair share of loud-spoken supporters. Coming from Django, naturally my first thought was that I wanted the PHP framework equivalent of it. After some fruitless googling I decided there was no such thing, and instead I decided the selection criteria to be something fast, light-weight, and PHP5-based.

With the help of posts like this, this, and this, I somewhat arbitrarily narrowed down the contenders to Kohana, Zend, and Yii, and ultimately picked Yii since it was the new kid on the block.

A few snags…
I ran into a few snags during my brief foray into PHP land with Tarzan and Yii so I thought I’d write them down here, just in case it might help someone facing the same issues as I did, or in case I run into them again myself. 🙂

  • There’s a bug in the stable version on Tarzan that makes it ignore any Amazon Associate IDs you supply in the configuration or the class constructors. Product links returned by the Amazon API will because of this not be tracked, which means you won’t get any revenue share from Amazon to your affiliate account.
  • Tarzan returns SimpleXML objects, but apparently it’s not possible to serialize PHP built-in objects. I learned this when I tried to put the data I got back from Tarzan uncasted into memcached, and got this perplexing error message on retrieval:

    unserialize() [function.unserialize]: Node no longer exists

  • I first had multiple class definitions per PHP file, and this worked fine with Yii and its autoload support. However, when I tried to put these objects into memcached I again got confusing errors when they were unserialized, e.g.:

    YiiBase::include(BrowseNode.php) [yiibase.include]: failed to open stream: No such file or directory

    The BrowseNode class was not defined in a file of its own, and I suppose that’s why it couldn’t be found. When I moved it into a separate BrowseNode.php file, things started to work.

  • Update: this note is not quite correct, please see the comments below this post! Something really weird happens when you try to use the CHtml class in Yii to output an image with an empty or missing URL. This will make the controller action execute twice! I have no idea why this happens but it took me a good while to track down the cause. To reproduce, add the line below to a view in your Yii application and add a log statement to the corresponding controller action:

Final words
Amazon’s product API really is a solid, fast, and comprehensive service that deserves all the praise it has received. With the new API name, Amazon today also announced that API requests in the future will have to be authenticated through a hash calculated for every request based on your AWS identifiers and the parameters of the request. This requirement is phased in over a period ending on August 15, 2009.

Tarzan obviously lacks support for this, but at least the author is aware of the change. Apart from this and the annoying Associate ID bug I mentioned previously, Tarzan worked great for me and I wouldn’t hesitate to use it again, seeing that it’s actively maintained and tries to stay on top of Amazon’s evolution of services.

As for Yii, I did not use it enough to give a proper verdict — I barely tested the ORM support for instance — but it was easy getting started and its MVC structure seemed logical enough, although the relative youth of the framework is visible in some rough edges here and there. Yii markets itself as a high-performance framework and although I don’t have that many reference points, the execution speed was more than satisfactory. Would I use it again? Probably, but I’ll check out Kohana too at some point.


7 responses to “Some notes on Amazon, Tarzan, and Yii

  1. The empty url image problem isn’t to do with Yii but any empty image tag if the browser encounters an empty image it just loads the current page again, it’s one of those odd quirks!

  2. devdoodles

    Oops, I believe you are correct! I obviously should have done this before, but I just verified by simply adding this line to a static html page and then serve it directly from the httpd server: <img src=”” alt=””>. As expected, the request is logged twice by the server. Thanks for pointing this out! I’ve updated the post accordingly.

  3. If you are looking for Django written in PHP, check out Pluf:

    It is an almost exact copy of Django.

  4. PyAWS is alive and kicking on bitbucket. Here’s a branch with the new authentication stuff:

  5. devdoodles

    Thanks for the update!

  6. Just a heads up — that Tarzan bug having to do with the Amazon Associates ID was fixed as part of Tarzan 2.0.4 back in May 2009.

  7. Thanks Ryan! I was using my own patched version up until recently, but it wasn’t very pretty. Regarding the AAWS authentication, it seems you’ve fixed that too in 2.0.5. Good stuff.