Android:在使用volley向laravel服务器发送数据时出现意外响应码500

我使用Volley作为我的应用程序的网络处理程序。我的后端是apache服务器上的Laravel 5。我正在尝试使用自定义请求POST，如下所述:Volley JsonObjectRequest POST请求不工作，但它保持500代码错误响应的错误。还有其他解决办法吗?还是我错过了什么?我对Laravel不熟悉。谢谢。

这是我的代码:

public class CustomRequest extends Request<JSONObject> {
    private Listener<JSONObject> listener;
    private Map<String, String> params;
    public CustomRequest(String url, Map<String, String> params,
                         Listener<JSONObject> reponseListener, ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        this.listener = reponseListener;
        this.params = params;
    }
    public CustomRequest(int method, String url, Map<String, String> params,
                         Listener<JSONObject> reponseListener, ErrorListener errorListener) {
        super(method, url, errorListener);
        this.listener = reponseListener;
        this.params = params;
    }
    protected Map<String, String> getParams()
            throws com.android.volley.AuthFailureError {
        Log.d("parameter", params.toString());
        return params;
    };

    @Override
    protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
        try {
            String jsonString = new String(response.data,
                    HttpHeaderParser.parseCharset(response.headers));
            return Response.success(new JSONObject(jsonString),
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        } catch (JSONException je) {
            return Response.error(new ParseError(je));
        }
    }
    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
        HashMap<String, String> headers = new HashMap<String, String>();
        //headers.put("X-CSRF-Token", params.get("_token"));
        headers.put("Content-Type", "application/x-www-form-urlencoded; charset=utf-8");
        //Log.d("token",params.get("_token"));
        return headers;
    }
    @Override
    protected void deliverResponse(JSONObject response) {
        // TODO Auto-generated method stub
        listener.onResponse(response);
    }
}

on main activity:

final String POST_URL = "https://www.pinus.com/api/registertoserver";
    final HashMap<String, String> postParams = new HashMap<String, String>();
    postParams.put("email", email);
    postParams.put("first_name", firstName);
    postParams.put("last_name", lastName);
    postParams.put("alamat", adress);
    postParams.put("notelp", phone);

    final RequestQueue queue = Volley.newRequestQueue(getApplicationContext(), new OkHttpStack());
    CustomRequest jsonObjReq = new CustomRequest(Request.Method.POST, POST_URL, postParams, new com.android.volley.Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                Log.d("result", response.toString());
                if (response.getBoolean("status")) {
                    //pDialog.dismiss();
                    finish();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new com.android.volley.Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
        }
    });
    // Adding request to request queue
    jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
            10000,
            DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
            DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
    queue.add(jsonObjReq);
    queue.start();