选择带有参数的查询，其中clausule with volley and PDO（Android）

我为我的应用程序提供了一个Web服务，在那里我查阅了必要的数据 . 返回表的所有数据的查询正常工作，但我需要根据android studio中变量的值显示数据 . 一切都在浏览器中正常工作（ULR中的参数），但在AS中没有 .

这是我与Volley的电话：

final String module = moduleContent; //this value is "coding"
StringRequest stringRequest = new StringRequest(Request.Method.GET, Constans.GET_SCHOOL_CONTENT,
    new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            Log.d(TAG, "onResponse: " + response);
            try {
                //converting the string to json array object
                JSONArray array = new JSONArray(response);

                //traversing through all the object
                for (int i = 0; i < array.length(); i++) {

                    //getting product object from json array
                    JSONObject schoolContent = array.getJSONObject(i);

                    //adding the product to product list
                    schoolContentList.add(new SchoolContent(
                            schoolContent.getString("module"),
                            schoolContent.getString("title"),
                            schoolContent.getString("content_url")
                    ));
                }

                //creating adapter object and setting it to recyclerview
                SchoolAdapter adapter = new SchoolAdapter(SchoolModuleActivity.this, schoolContentList);
                recyclerView.setAdapter(adapter);
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {

    }
}){
    @Override
    public Map<String, String> getParams() throws AuthFailureError {
        Map<String, String> params = new HashMap<>();
        params.put("module", module);
        return params;
    }
};

VolleySingleton.getInstance(getApplicationContext()).addToRequestQueue(stringRequest);

这是我的PHP代码：

public static function getByModule($module){
    $consulta = "SELECT module, title, content_url FROM " .self::table_name." WHERE module = ?";
    //$consulta = "SELECT module, title, content_url FROM " .self::table_name." WHERE ".self::$module." = " .$module;

    try {
        $comando = DatabaseConnection::getInstance()->getDb()->prepare($consulta);

        $comando->execute([$module]);

        return $comando->fetchAll(PDO::FETCH_ASSOC);

    } catch (PDOException $e) {
        return $consulta;
    }
}

前一个是类，对函数的调用是这样的：

require '../data/school_content.php';

if ($_SERVER['REQUEST_METHOD'] == 'GET') {

    $module = $_GET['module'];
    $content = school_content::getByModule($module);

    header('Content-Type: application/json');

     print json_encode($content);

}

AS中的结果：