how to remove the error showing below:(laravel framework) - php

Question

I have viewed a lot off documents already. I am trying to do my login, but its not working. Showing errors. I don't know the reason.i am very new in laravel
This is my controller code
public function do_login()
{
$credentials = [
'username'=>Input::get('username'),
'password'=>Input::get('password')
];
$rules = [
'username' => 'required',
'password'=>'required'
];
//validating the credentials.
$validator = Validator::make($credentials,$rules);
//in case the credentials are valid. Try to login the user.
if($validator->passes())
{
if (Auth::attempt($credentials))
{
//if successfull redirect the user
return Redirect::to('home');
}
else
{
//else send back the login failure message.
return Redirect::back()->withInput()->with('failure','username or password is invalid!');
}
}
else
{
//send back the validation errors.
return Redirect::back()->withErrors($validator)->withInput();
}
}
this is my model code:
<?php namespace LARAVEL\laravel_1st_project\models\UserModel;
use Illuminate\Auth\UserInterface;
use Illuminate\Auth\Reminders\RemindableInterface;
class UserModel extends \Eloquent implements UserInterface , RemindableInterface
{
public $table = "user";
protected $primaryKey = 'employee_id';
//public $timestamps = false;
}
this is my app\config\auth.php :
'model' => 'LARAVEL\laravel_1st_project\UserModel',
'table' => 'user',
'reminder' => array(
'email' => 'email.auth.reminder',
'table' => 'password_reminders',
'expire' => 60,
),
Error :