Steph-
One thing to check is that all paths in your php.ini file are relative paths (extension_dir, include_path, etc.). I've found that with absolute paths, an app runs fine in the dev fabric, but not when you deploy it.
If that's not the problem, let me know...I'll have to think about how to capture log information.
Hope that helps.
-Brian
Edit: In lieu of writing PHP errors to a file or blob, you could just display errors on your pages (since you are just testing, this should be OK). Adding something like this to your scripts will display errors:
error_reporting(E_ALL);
ini_set('display_errors', 'On');
And, you can update these setting without redeploying...details here:
http://blogs.msdn.com/b/brian_swan/archive/2011/04/11/updating-php-settings-in-windows-azure.aspx.
This posting is provided "AS IS" with no warranties, and confers no rights. http://blogs.msdn.com/brian_swan