You may refer to this JSFiddle to see how it works: http://jsfiddle.net/wZsGc/
I'm using the JSFiddle Echo JSONP service, to simulate the output I require.
Your PHP output must be similar to:
Now the reason I'm using:
response.result = JSON.parse(response.result);
Because jsfiddle outputs Stringified, thus I'm parsing it. If your PHP output is similar to the above output, then parsing isn't required.
And you may not require to submit data to your PHP, but I'm submitting the data I want back to the echo service.