允许片段未设置的JSON选项

I can see this question has been asked before but can't find that anyone has accepted an answer anywhere. My error is:

NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.

let myUrl = NSURL(string: "http://www.example.com/xxx.php")
    let request = NSMutableURLRequest(URL:myUrl!);
    let session = NSURLSession.sharedSession()
    request.HTTPMethod = "POST";

    let postString = "email=\(useremail)&pass=\(userpassword)&username=\(username)"
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
    let task = session.dataTaskWithRequest(request) { (data, response, error) in
        // if error
        if error != nil {
            print("error=\(error)")
            return
        }

        var json: NSDictionary? = nil
        do {
            json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) as? NSDictionary
        } catch {
            print("error=\(error)")
        }
                  if let parseJSON = json {

            let resultvalue = parseJSON["status"] as? String
            print("result: \(resultvalue)")


        var isuserregistered:Bool = false;
        if(resultvalue=="Success") { isuserregistered = true; }

        var messagetodisplay:String = parseJSON["message"] as! String!;
        if(!isuserregistered)
        {
            messagetodisplay = parseJSON["message"] as! String!;

            }}

I am trying to send email, pass, username, and successfully presenting my alert and changing view controller. but I am yet to hit database. It's PHP and MYSQL via url.