Active Record "insert" is not working properly

Code:

&lt;?php

class Register extends CI_Controller {

    public static $step;

    public $data;

    public function __construct(){

        parent::__construct();    

        $this->step = 1;



    }

    public function index(){

                $this->data['name_username'] = "username";

        $this->data['name_password'] = "password";

        $this->data['name_repassword'] = "password2";

        $this->data['name_email'] = "email";

        $this->data['name_submitBtn'] = "regBtn";

        $this->data['title'] = "Register";

        $this->template->render($this->data);

    }

    public function process(){

        $this->load->helper('security');

        $username = $this->input->post("username");

        $passwd = do_hash($this->input->post("password"));

        $email = $this->input->post("email");    

        $sql = array(

        'username' => $username,

        'password' => $passwd,

        'email' => $email

        );

        $this->db->insert('members', $sql)



        $this->data['title'] = "Registration done!";

        $this->data['msg'] = "A private key of your account has been sent to your email address. Please, enter it in below form to confirm your account.";

            $this->template->render($this->data);

    }

}

?&gt;

Code:

{header}

<h1>{title}</h1>

<p>

{msg}

</p>

{footer}

Code:

public function process(){

        $this->load->helper('security');

        $username = $this->input->post("username");

        $passwd = do_hash($this->input->post("password"));

        $email = $this->input->post("email");    

        $this->load->model('members'); 

        $this->members->register($username, $passwd, $email);  

        $this->data['title'] = "Registration done!";

        $this->data['msg'] = "A private key of your account has been sent to your email address. Please, enter it in below form to confirm your account.";

            $this->template->render($this->data);

    }

Code:

&lt;?php

class Members extends CI_Model {

    public function register($username, $password, $email){

        $sqlq = "INSERT INTO members VALUES(?, ?, ?, ?)";

        $this->db->query($sqlq, array(NULL, $username, $password, $email));    

    }

}

?&gt;

Code:

&lt;?php

class Setting {

    private $CI, $value;

    public function __construct(){

        $this->CI = & get_instance();

        $this->CI->load->database();

    }

    public function add($option, $value){

            $data = $this->get(array($option));

            if(isset($data[$option])){

                    $this->update($option, $value);

            }

            else {

                $sql = "INSERT INTO config VALUES(?, ?)";

                $this->CI->db->query($sql, array($option, $value));

            }

    }

    public function update($option, $value){

        $sql = "UPDATE config SET value=? WHERE ukey=?";

        $this->CI->db->query($sql, array($value, $option));    

    }

    public function _get($option = ""){

        $sql = "SELECT * FROM config WHERE ukey = ?";

        $result = $this->CI->db->query($sql, array($option));    

        $this->value = $result->row_array();

        return $this->value['value'];        

    }

    public function get($options = array(), $parse = FALSE){

        $data = array();

        $i = 0;

        foreach($options as $option){

            if($parse == FALSE)

                $data[$option] = $this->_get($option);

            else 

                $data[$i++][$option] = $this->_get($option);    

        }

        return $data;

    }

}

?&gt;

Code:

user_validated = 0;

passwd_validated = 0;

function user_available(){

    $.ajax({

          type: "POST",

         url: "http://localhost:8888/ptcan/index.php/ajax/username_available/"+$("#username").val(),

          success: function(msg){

            if(msg == 1){

                $("#username_status").html("<font class=\"succ\">"+$("#username").val()+" is available!</font>");

                user_validated = 1;

                 reg_validate();

            }

            else {

                $("#username_status").html("<font class=\"err\">"+$("#username").val()+" is not available, try again!</font>");

                user_validated = 0;    

                 reg_validate();

            }

        }

     })

    

}

function pass_check(){

    if(($("#password").val() != $("#password2").val())){

                $("#password_error").html("<span class=\"err\">Password do not matches!</span>");

                passwd_validated = 0;

    }

    else {

        $("#password_error").html("<span class=\"succ\">Password matched!</span>");

        passwd_validated = 1;

    

    }

    reg_validate();

}

function reg_validate(){

    if((user_validated == 1) && (passwd_validated == 1))

        $("#regBtn").css("display", "block");

    else

        $("#regBtn").css("display", "none");

}

Code:

&lt;?php

class Ajax extends CI_Controller {

    public function __construct(){

        parent::__construct();    

    }

    public function username_available($username = ""){

        if($username != ""){

            $q = $this->db->query("SELECT username FROM members WHERE username = ?", array($username));

            if($q->num_rows() == 0){

                echo "1";

            }

            else {

                echo "0";

            }

        }

        else {

            echo "<span class=\"err\">Username is required!</span>";    

        }

    }

}

?&gt;