我已经创建了一个laravel应用程序来存储员工数据，但当我提交表单时，它给了我以下错误，我应该做些什么来避免这个问题。谢谢

这是我的EmployeeController存储方法

public function store(Request $request)
{
        $this->validate($request,array(
            'lastname'=>'required|max:60',
            'firstname'=>'required|max:60',
            'middlename'=>'required|max:60',
            'address'=>'required|max:120',
            'NIC'=>'required|max:10',
            'city_id'=>'required|max:60',
            'state_id'=>'required|max:60',
            'mobile'=>'required|max:10',
            'email'=>'required|max:60',
            'postal_code'=>'required|max:10',
            'birthdate'=>'required|date',
            'date_hired'=>'required|date',
            'department_id'=>'required|max:10',

    ));
    $employee = new Employee();
    $employee->lastname=$request->lastname;
    $employee->firstname=$request->firstname;
    $employee->middlename=$request->middlename;
    $employee->address=$request->address;
    $employee->NIC=$request->NIC;
    $employee->city_id=$request->city_id;
    $employee->state_id=$request->state_id;
    $employee->mobile=$request->mobile;
    $employee->email->$request->email;
    $employee->postal_code=$request->postal_code;
    $employee->birthdate=$request->birthdate;
    $employee->date_hired=$request->date_hired;
    $employee->department_id=$request->department_id;

    $employee->save();
}

表格页眉

{!! Form::open(['route'=>'employee.store','class'=>'form-horizontal p-t-20']) !!}

用于控制器的类

namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Department;
use Illuminate\Support\Facades\DB;
use App\Employee;