check the response of a php function

check the response of a php function

I'm stuck!:(

When I click on a link I have this event:
$.ajax({type: "POST",
     url: "/req.php",
     asynchronous: false,
     dataType: "xml",
     data: "jQuery=1"+
              "&op=attivaProva"+
              "&modulo=statistiche",
     success: function(risultato){
                     if (risultato) {
                        jAlert('Attivazione eseguita con successo', 'Complimenti!', function(){
                                                    window.location.reload();
                                                });
                                            }else{
                                                jAlert('Error','Error');
                                            }

                                        }
                    });


The php file check the "op" and call a function that return true (if the query is ok) or false (if the query is not ok). What I have to do to test this value? I mean....jQuery make the sync call, call the php script that run a INSERT query. I need to test in jquery if this QUERY was correctcly lanced. I try with the code above but I can understand that the success parameter is only for the good call of the php script, not for the response.
What I have to do?
Thanks