autoloading helper library model breake ajax json

no, i don't call get_instance(), here is the code of the helper

PHP Code:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

    if(!function_exists('load_js')){
        function load_js($scripts,$init){
            $result = "
            <script type='text/javascript'>
                var deferredJSFiles = [
                '//code.jquery.com/jquery-2.1.4.min.js',
                '//cdnjs.cloudflare.com/ajax/libs/jquery.matchHeight/0.6.0/jquery.matchHeight-min.js',";
            $result .= "'".base_url('assets/js/jquery-ui.min.js')."',";
            $result .= "'".base_url('assets/js/jquery.cookiebar.min.js')."',";
            $result .= "'".base_url('assets/js/classie.min.js')."',";
            $result .= "'".base_url('assets/js/jquery.mmenu.min.all.js')."',";
            $result .= "'".base_url('assets/js/behavior.js')."'";
            $result .= $scripts;
            
            $result .= "];
                function downloadJSAtOnload() {
                    if (!deferredJSFiles.length) return;
                    var deferredJSFile = deferredJSFiles.shift();
                    var element = document.createElement('script');
                    element.src = deferredJSFile;
                    element.onload = element.onreadystatechange = function() { if (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete') downloadJSAtOnload(); };
                    document.body.appendChild(element);
                    if(deferredJSFiles.length == '0'){";
            $result .= $init;
            $result .= "}
                }
                if (window.addEventListener) window.addEventListener('load', downloadJSAtOnload, false);
                else if (window.attachEvent) window.attachEvent('onload', downloadJSAtOnload);
                else window.onload = downloadJSAtOnload;
            </script>";
            return $result;
        }
    } 


and i have the same problem when i try to auto load this model

PHP Code:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Menu_model extends CI_Model{
    
    public function menuPlace($place){
        $res        = $this->db->conn_id->prepare('SELECT * FROM `menu` WHERE  `place` = :place');
        $res->bindParam(':place', $place, PDO::PARAM_INT);
        $res->execute();
        $result     = $res->fetchAll(PDO::FETCH_ASSOC);
        return $result;
    }
    
    public function menuRewrite($rewrite){
        $res        = $this->db->conn_id->prepare('SELECT * FROM `menu` WHERE  `rewrite` = :rewrite');
        $res->bindParam(':rewrite', $rewrite, PDO::PARAM_INT);
        $res->execute();
        $result     = $res->fetchAll(PDO::FETCH_ASSOC);
        return $result;
    }
    
    
}