Jquery :: Json Response From An Ajax Request ?

I got a problem with a json response from an ajax request.

I have the following code :

Code:

And the called page (ajax_sous_famille.php) is giving me this result :

Code:

The info in the resulting string is correct, but here you can see the [ ] at the start and end of the line. It seems not to be a correct Json string and then it crashes my script !

I have another request like this which gives me the good format of resulting data (without the [ ]) and which works perfectly when i decode the Json string to display it.

The difference between the 2 requests is that the one which works returns only 1 array of values like

Code:

And the second one which doesn't work returns something like

Code:

Actually, all the records are coming from a database and in the case it doesn't work, i wanna get several results from this database.