有时post数据返回null、Jquery、PHP

我正在尝试将数据从PHP发布到服务器，该服务器是使用jquery在java中构建的，它使用json进行响应。 遵循PHP，Jquery发布代码

    <script  type="text/javascript" charset="utf-8">

    $(function() {
        // wire up the buttons to dismiss the modal when shown
    $("#dialog-form").bind("show", function() {
        $("#dialog-form #add-ques").click(function(e) {
            // do something based on which button was clicked
            // we just log the contents of the link element for demo purposes
            $.post('question_data.php', $("form#gform").serialize(), function(data) {


                             if(data.result=="true"){
                                     //window.location=+data.lastId;
                                    console.log(data);

                                 }else{

                                     $("#dialog-form").modal('hide');

                                 }

                         },"json");

            // hide the dialog box
            $("#dialog-form").modal('hide');

        });

    }); 

</script>

JSON O/p

    {"result": "true","lastId": 86}

---

上面的代码有时运行得很好，但有时返回空值。无法跟踪此问题

感谢您的回复@ubercooluk。。仍然返回null值not error（即您的帖子有一些问题），这是用jquery在java中构建的

//Track it on the server side

if($type=="save"){
        $surveyname= htmlspecialchars(trim($_POST["name"]));
        $company_id= htmlspecialchars(trim($_POST["company_id"]));
        $flag = 1;
        if($surveyname == null || $surveyname == ""){
          $flag = 0;
        }
        if($company_id == null || $company_id == ""){
          $flag = 0;
        }

    if($flag){
        $result = json_decode(file_get_contents("http://localhost:8080/mobsurvey/survey/new/?name=$surveyname&company_id=$company_id"));
        $arr = array('result' => $result->result, 'lastId' => $result->lastId);

        header('Content-type: text/json');
        header('Content-type: application/json');


      }else{
    $arr = array('Your post has some problems..not posting some of the values');
    }
      echo json_encode($arr);
    }

    {"result": "true","lastId": 86}

//Track it on the server side

if($type=="save"){
        $surveyname= htmlspecialchars(trim($_POST["name"]));
        $company_id= htmlspecialchars(trim($_POST["company_id"]));
        $flag = 1;
        if($surveyname == null || $surveyname == ""){
          $flag = 0;
        }
        if($company_id == null || $company_id == ""){
          $flag = 0;
        }

    if($flag){
        $result = json_decode(file_get_contents("http://localhost:8080/mobsurvey/survey/new/?name=$surveyname&company_id=$company_id"));
        $arr = array('result' => $result->result, 'lastId' => $result->lastId);

        header('Content-type: text/json');
        header('Content-type: application/json');


      }else{
    $arr = array('Your post has some problems..not posting some of the values');
    }
      echo json_encode($arr);
    }