I think of myself first and foremost as a PHP developer but serious sites are getting more and more JS-heavy as time goes on so it gets harder (and less pragmatic) to try and avoid dealing with JSPHP communication of some sort.
I'm a big advocate of RESTful design so tend to end up attempting to write scripts that do lots of GETs and POSTs (as appropriate) and parsing out whatever custom response format I've decided JSON requests will return. It feels good - like I'm sticking to my principles and 'doing it right' but it's a long painful slog that can feel like self-flagellation at times.
It's also slow and hard to prototype - it's hard to argue in favour of some abstract design idea when it's making you take forever to generate simple tasks . Sometimes when I feel lazy what I really want is a way of calling my PHP objects directly from the JS and not worrying about what's happening in the underlying HTTP, and that's what JSON-RPC provides.
In this blog I'll be showing some simple examples of JSON-RPC in action but first let's look at the pros and cons.