Gonzalo Ayuso takes his "CouchDb as a filesystem" approach one step further (see the previous post about it here) with this new post talking about monkey patching to store files into the CouchDb server using the normal PHP file handling functions.
Since PHP5.3 a new design pattern is available for us: Monkey Patching. With this pattern we can override PHP's core functions with a home-made functions in a different namespace (another example here). That's means if I have fopen function in the above example, PHP uses the filesystem function "fopen" but if we set a namespace in our example, PHP will search first the function within the current namespace.
By defining the new interface inside of a namespace (with functions to override the default PHP file handlers) you can have the rest of the code call the same functions (fopen, fread, etc) but they'll do different things. In this case it handles them as push and pull to the CouchDb instead of the normal filesystem. You can grab the source for this example here.