具有Volley和PHP的Android JSON在字符0处输入结束

I am writing an app that requires the use of storing contacts in a database so I am using wammp and PHPMyAdmin to write a simple REST API. I have written the parts that involve registering and logging in but for some reason I can not get the storing of contacts to work even though I thought it would be almost the same thing verbatim. I am getting the exception:

org.json.JSONException: End of input at character 0 of

I have looked around all over for this issue and it looks to be like the JSON that I am passing back to my app is empty, so I am aware of the problem but everywhere that I looked, the solutions did not help me actually fix the problem so I feel like it may be a unique problem. Here is my relevant Android code:

// Create the new string request
StringRequest stringRequest = new StringRequest(Request.Method.POST, AppConfig.URL_NEW_CONTACT, new Response.Listener<String>()
{
    @Override
    public void onResponse(String response)
    {
        // Log method entry
        MethodLogger methodLogger = new MethodLogger();

        // Log the JSON that was returned
        methodLogger.d("New Contact Response: " + response.toString());

        // Remove the processing view
        hideDialog();

         // Try to retrieve JSON and parse through it
         try
         {
             JSONObject jObj = new JSONObject(response);

             // Check for errors in the JSON passed back
             boolean error = jObj.getBoolean("error");

             /*----------------------------------------------------------------*
              *  If there was no error found                                   *
              *----------------------------------------------------------------*/
              if (!error)
              {
                  // Indicate the success to the user
                  Toast.makeText(getApplicationContext(), "Contact successfully created.", Toast.LENGTH_LONG).show();

                  // Take the user back to the contact page
                  routeToContactPage();
              }

              /*----------------------------------------------------------------*
               *  Else if there was an error found                              *
               *----------------------------------------------------------------*/
               else
               {
                   // Notify the user
                   String errorMsg = jObj.getString("message");
                   Toast.makeText(getApplicationContext(),
                                      errorMsg, Toast.LENGTH_LONG).show();
               }
            }

            /*--------------------------------------------------------------------*
             * Catch any error in retrieving parsing etc JSON                     *
             *--------------------------------------------------------------------*/
             catch (JSONException e)
             {
                 e.printStackTrace();
                 Toast.makeText(getApplicationContext(), "Error storing contact: " + e.getMessage(), Toast.LENGTH_LONG).show();
             }

             // Log method exit
             methodLogger.end();

         }
     }, new Response.ErrorListener()
     {
         @Override
         public void onErrorResponse(VolleyError error)
         {
              // Log method entry
              MethodLogger methodLogger = new MethodLogger();

              // Notify the user
              methodLogger.e("Error storing contact: " + error.getMessage());
              Toast.makeText(getApplicationContext(),
                                     error.getMessage(), Toast.LENGTH_LONG).show();
              hideDialog();

              // Log method exit
              methodLogger.end();
          }

      })
      {
           @Override
           protected Map<String, String> getParams()
           {
               // Log method entry
               MethodLogger methodLogger = new MethodLogger();

               // create a new params object and add the contact data
               Map<String, String> params = new HashMap<String, String>();

               // Add the params to the volley request
               params.put("user_id", SessionManager.getUser().getId());
               params.put("name", name);
               params.put("email", emailAddress);

               // Log method exit
               methodLogger.end();

               // Return the user data
               return params;
           }

      };

      // Send the request string to the request queue to be sent to the PHP API
      AppController.getInstance().addToRequestQueue(stringRequest, tag_string_req);
}

Relevant PHP Code:

Store the contact:

public function storeContact($name, $email, $user_id) 
{
    $uuid = uniqid('', true);

    $result = mysqli_query($this->conn, "INSERT INTO contacts (unique_id, name, email, created_at, updated_at, user_id) VALUES ('$uuid', '$name', '$email', NOW(), NULL, '$user_id')") or die (mysql_error());

    if ($result) 
    {
        $contact = mysqli_query($this->conn, "SELECT * FROM contacts WHERE name = '$name' AND user_id = '$user_id'");

        return $contact;
    } 
    else 
    {
        return false;
    }
}

Communicate with the server/app:

<?php

require_once 'include/DB_Functions.php';
$db = new DB_Functions();

$response = array();

if (isset($_POST['user_id']) && isset($_POST['name']) && isset($_POST['email'])) 
{
    $user_id = $_POST['user_id'];
    $name = $_POST['name'];
    $email = $_POST['email'];

    $result = $db->storeContact($name, $email, $user_id); 

    if ($result) 
    {
        $response["error"] = FALSE;
        $response["message"] = "Contact stored successfully";
    } 
    else 
    {
        $response["error"] = TRUE;
        $response["message"] = "Unknown error occurred in storing contact";
    }
} 
else 
{
    $response["error"] = TRUE;
    $response["message"] = "Required parameters, name, email, or user_id, missing";
}

echo json_encode($response);

?>

and finally, relevant logcat output:

07-30 22:39:07.408 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.AppController: Method Entry: getInstance()
getInstance() finished in 0.000 seconds.
Method Entry: addToRequestQueue()
07-30 22:39:07.409 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.AppController: Method Entry: getRequestQueue()
getRequestQueue() finished in 0.000 seconds.
07-30 22:39:07.410 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.AppController: addToRequestQueue() finished in 0.001 seconds.
07-30 22:39:07.410 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.ContactActivity: onCreate() finished in 0.072 seconds.
07-30 22:39:07.424 24212-31569/com.example.e4977.spotme D/com.example.e4977.spotme.ContactActivity$3: Method Entry: getParams()
07-30 22:39:07.425 24212-31569/com.example.e4977.spotme D/com.example.e4977.spotme.ContactActivity$3: getParams() finished in 0.000 seconds.
07-30 22:39:07.426 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.NewContactActivity$1$1: Method Entry: onResponse()
onResponse() New Contact Response: 
07-30 22:39:07.426 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.NewContactActivity: Method Entry: hideDialog()
07-30 22:39:07.448 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.NewContactActivity: hideDialog() finished in 0.021 seconds.
07-30 22:39:07.448 24212-24212/com.example.e4977.spotme W/System.err: org.json.JSONException: End of input at character 0 of 
    at org.json.JSONTokener.syntaxError(JSONTokener.java:449)
    at org.json.JSONTokener.nextValue(JSONTokener.java:97)
    at org.json.JSONObject.<init>(JSONObject.java:159)
    at org.json.JSONObject.<init>(JSONObject.java:176)
    at com.example.e4977.spotme.NewContactActivity$1$1.onResponse(NewContactActivity.java:119)
07-30 22:39:07.449 24212-24212/com.example.e4977.spotme W/System.err:     at com.example.e4977.spotme.NewContactActivity$1$1.onResponse(NewContactActivity.java:99)
    at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
    at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
    at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
    at android.os.Handler.handleCallback(Handler.java:789)
    at android.os.Handler.dispatchMessage(Handler.java:98)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6798)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
07-30 22:39:07.454 24212-24212/com.example.e4977.spotme D/com.example.e4977.spotme.NewContactActivity$1$1: onResponse() finished in 0.027 seconds.

Its also worth it to note that I see that the response is empty, I however do not know why. Here is the Database Schema in case that is part of the problem too.

DBSchema