CodeIgniter基本URL不在实时服务器上工作

i have a php codeignitor php app which was working fine on localserver xampp but when i uploaded that app on a live server, its not loading assets, images and also not submitting the login form. When see the source for login page, it shows urls like this

<link href="<?=base_url()?>assets/css/bootstrap.min.css" rel="stylesheet">
<link href="<?=base_url()?>assets/css/datepicker3.css" rel="stylesheet">
<link href="<?=base_url()?>assets/css/styles.css" rel="stylesheet">

also the form action shows like that

<form action="<?=base_url()?>auth/login" method="post">

i have tried every thing url helpers and all that stuff but still unable to fix it.

Sorry if is too obvious, but I assume that you have the url helper loaded in your autoload, right?