I am new to jqgrid and I'm trying to get cell editing against a remote server working.

To me, it is not clear from the documentation or examples what the server should return in response to cell edit ajax requests. I can submit and perform a database update okay, but if there is a database error, what ever I return from the server, the grid updates. The only way I have found to display an error is to set the HTTP response code to 400 or 500 range, but can return no useful error message.

How do I return a meaningful server error and display it?

Using php & JSON the best I can work out from the documentation is something like this, is this correct?