查询在代码点火器中不起作用

i am developing this login system with admin. i am currently making the model for verifying the usertype, (admin or user) but the query does not work, while its almost the same as the one with account verification. i checked if the post parameter is returned to the second query, and it is, but it is still not working. but the good part is, if i hard coded the username, it works perfectly. please help. here is my code

login_model.php

public function can_log_in(){

    $sql ="SELECT * FROM tbl_users WHERE USERNAME = ? AND PASSWORD = ?";
    $data = array(
        'USERNAME' => $this->input->post('USERNAME'),
        'PASSWORD' => $this->input->post('PASSWORD')
        );
    $query = $this->db->query($sql, $data);

//$result = $query->result_array();
//print_r($result);
//exit;
    if ($query->num_rows() == 1){

        return true;

    }else{

        return false;
    }

}

public function returnQuery(){

    ////hard coded (works perfectly)

    //$sql ="SELECT USERCODE FROM tbl_users WHERE USERNAME = 'username' AND PASSWORD = 'password'";
    //$query = $this->db->query($sql);
    //$result = $query->result_array();

///database based.

    $sql ="SELECT USERCODE FROM tbl_users WHERE USERNAME = ? AND PASSWORD = ?";
    $data = array(
        'USERNAME' => $this->input->post('USERNAME'),
        'PASSWORD' => $this->input->post('PASSWORD')
        );


//print_r($data);exit;

    $query = $this->db->query($sql, $data);

    //print_r($query);exit; ->> output is an empty array


$result = $query->result_array();
//print_r($result);exit;


    if(count($result) > 0){
       return $result[0]["USERCODE"];
    }else{
      return 0;
    }
}

try this and please make sure the $this->input->post('USERNAME') and $this->input->post('PASSWORD') contains data.

$sql ="SELECT * FROM tbl_users WHERE USERNAME = ? AND PASSWORD = ?";
    $data = array(
            $this->input->post('USERNAME'),
            $this->input->post('PASSWORD')
        );
    $query = $this->db->query($sql, $data);

The method should be like this

public function can_log_in(){

    $sql ="SELECT * FROM tbl_users WHERE USERNAME = ? AND PASSWORD = ?";
    $data = array(
              $this->input->post('USERNAME'),
              $this->input->post('PASSWORD')
            );

    $query = $this->db->query($sql, $data);

    if ($query->num_rows() == 1){

        return true;

    }else{

        return false;
    }

}

and your returnQuery might be like this

public function returnQuery(){


    $sql ="SELECT USERCODE FROM tbl_users WHERE USERNAME = ? AND PASSWORD = ?";
    $data = array(
             $this->input->post('USERNAME'),
             $this->input->post('PASSWORD')
           );
    $query = $this->db->query($sql, $data);
    $result = $query->result_array();

    if($query->num_rows() > 0){
       return $result[0]["USERCODE"];
    }else{
      return 0;
    }
}

Hope that helps.