表单验证CI不适用于所有字段

here is the controller

class Form extends CI_Controller {

function index()
{
    $this->load->helper(array('form', 'url'));

    $this->load->library('form_validation');

    $config = array(
           array(
                 'field'   => 'username',
                 'label'   => 'Username',
                 'rules'   => 'trim|required|min_length[5]|max_length[12]|is_unique[users.username]|xss_clean'
              ),
           array(
                 'field'   => 'password',
                 'label'   => 'Password',
                 'rules'   => 'trim|required|matches[passconf]|md5'
              ),
           array(
                 'field'   => 'passconf',
                 'label'   => 'Password Confirmation',
                 'rules'   => 'trim|required'
              ),   
           array(
                 'field'   => 'email',
                 'label'   => 'Email',
                 'rules'   => 'trim|required|valid_email|is_unique[users.email]'
              )
        );

    $this->form_validation->set_rules($config); 

    if ($this->form_validation->run() == FALSE)
    {
        $this->load->view('myform');
    }
    else
    {
        $this->load->view('formsuccess');
    }
}
}
?>

and here is the views (myform.php , formsuccess.php)

myform.php

<html>
<head>
<title>My Form</title>
</head>
<body>
<?php echo validation_errors(); ?>
<?php echo form_open('form'); ?>
<h5>Username</h5>
<input type="text" name="username" value="" size="50" />
<h5>Password</h5>
<input type="text" name="password" value="" size="50" />
<h5>Password Confirm</h5>
<input type="text" name="passconf" value="" size="50" />
<h5>Email Address</h5>
<input type="text" name="email" value="" size="50" />
<div><input type="submit" value="Submit" /></div>
</form>
</body>
</html>

formsuccess.php

<html>
<head>
<title>My Form</title>
</head>
<body>
<h3>Your form was successfully submitted!</h3>
<p><?php echo anchor('form', 'Try it again!'); ?></p>
</body>
</html>

after i run it, the validation works if the username not meet the requirements, but when username meet the requirements, the validation not work and go to success page, it should be work for all field on form, not just username. what should i do? sorry for my bad english

formigniter.org/app

I prefer to use this, it automatically add validations.