Quercus really is great stuff; it allows nitwits like me to develop crappy PHP-applications and to deploy them on Google’s App Engine. But when you combine the limitations of Quercus’ PHP implementation with those of GAE, you’re going to have to code around some problems you wouldn’t be facing when developing a “normal” PHP webapp.
One example based on my limited experience (while writing a scanner service to detect “foreign” objects in websites for my future wp-privacy plugin): I had a CSV-file that had to be downloaded & parsed. Normally you would fopen the remote file and than use fgetcsv retrieve all data line per line. Or, if you’d prefer, you could fetch the file with mighty CURL and parse it using str_getcsv. But those approaches don’t work when in Quercus on GAE; fopening remote files doesn’t work (blame GAE) and while you can Curl the CSV into a variable, there’s no str_getcsv in Quercus (yet).
So I did what any self-respecting non-developer would do; I cried for help on StackOverflow. Some of the advice I got there involved obscure tricks like using data-uri’s, fopening php://memory or using SplTempFileObject, but none of those solutions produced anything but errors. So no built-in CSV-parsing for me, but (simple) “manual” parsing of the CSV in a string. Not a huge problem by any measure, but I’m sure there’s a whole lot more limitations, if only for all those functions that rely on file handles. But at least we’re having fun, no? ;-)
There isn’t a whole lot of documentation about running PHP on Google App Engine to be found, but these links may be helpful (in a “note to self: I should try this when I find the time” kind of way):
If you stumble on these pages because you’re thinking about creating and deploying a PHP application on Google App Engine, you should take into account that although Quercus looks promising, there are bound to be bugs that you’ll sooner or later run into. There are, for example, issues with determining file length and there are problems with variable referencing in some rare/ complex cases. You have been warned! ;-)
So you’re a wanna-be developer who’d love to deploy in the cloud, but you only “know” PHP? Well, as you might already have read elsewhere Caucho, the company behind Resin, has a 100% Java GPL’ed implementation of PHP5 called Quercus that can be used to run PHP on GAE. It took me some time to put the pieces of the puzzle together, but in the end it’s pretty straightforward.
From scratch to a deployed webapp in 7 steps:
- Download & install the Google App Engine SDK
- Download this GAE project template for PHP and unzip it in the root of the SDK directory as projects/phptemplate/
- Put your PHP-files in projects/phptemplate/war/ (you probably want to overwrite index.php and remove phpinfo.php)
- Test you application locally with dev_appserver as described here
- Login on https://appengine.google.com/ and register a new application
- Put the app id from (5) in projects/phptemplate/war/WEB-INF/appengine-web.xml, between the <application>-tage
- Upload your application as described here: appcfg –enable_jar_splitting update <path-to-war> (–enable_jar_splitting is needed as the WEB-INF/lib/resin.jar is rather big)
And there you have it, your very own PHP-app on GAE! Check out the Quercus info on on how you can access Java components from within you PHP-code, it might come in very handy to use GAE’s Java API’s for the datastore, queues and all those other goodies!
(Disclaimer: while this here template seems to work, I can’t make any promises or provide any kind of warranty. As soon as you download it, you assume all responsibilities for any problems you might cause to the Internet, GAE or the Ozone-layer.)