Thanks for the reply stworthy. Of course, I'd seen the demo and tried every possible variation of it I could think of - with and without the square brackets, trying to set the returned data into a javascript variable and then use the 'data' parameter to populate the property grid, etc and none of them worked. The behavior I was consistently seeing was that if I saved the results to a file called returndata.json and then served up that file to the URL parameter, it would work - but if i set the url to returndata.php, it would fail - and when I opened the .php file in a browser directly and did a view source - the data displayed *exactly* matched the data in the .json file (right down to crlf characters and encoding). I
However - since you took the time to reply to my question, I decided to humor you and rebuild my test using your example from the documentation so I could tell you exactly where it was failing...except this time it didn't fail....

ARGH!!! I've spent a month on this problem and it turns out the documentation was right all along? I'm guessing that in my earlier testing, there must have been a PHP error or info message that was invisibly getting in the way?
In any case - thanks very much for your reply and for setting me straight. None of the examples actually showed how to generate the json data via code so I wasn't completely sure I was generating it in the correct format. I thought I might need one extra set (or one fewer set) of quotes, curly brackets or square brackets - or some special html tag to surround the data - but now that I've finally seen it work, I'll be able to move forward. I was having a similar issue with several datagrid controls and I'm sure I will also be able to move forward with them now too!
Thanks again for taking the time to respond to such a simple question!