在将记录添加到数据库时,如何链接页面

I am trying to add records to the database using laravel. When I click on register, I am redirected to a nee page but I get an error saying page has expired due to inactivity. The record isn't inserted into the database.

The files are as follows:

register.blade.php

<form action="/registers" method="post">
<input type="hidden" name="_token" value="<?php echo csrf_token(); ?>">
  <div class="form-group has-feedback">
    <input type="text" class="form-control" name="username" placeholder="Full name">
    <span class="glyphicon glyphicon-user form-control-feedback"></span>
  </div>
  <div class="form-group has-feedback">
    <input type="email" class="form-control" name="email" placeholder="Email">
    <span class="glyphicon glyphicon-envelope form-control-feedback"></span>
  </div>
  <div class="form-group has-feedback">
    <input type="number" class="form-control" name="contact" placeholder="Contact Number">
    <span class="glyphicon glyphicon-earphone form-control-feedback"></span>
  </div>
  <div class="form-group has-feedback">
    <input type="password" class="form-control" name="pass" placeholder="Password">
    <span class="glyphicon glyphicon-lock form-control-feedback"></span>
  </div>
  <div class="form-group has-feedback">
    <input type="password" class="form-control" name="secondpass" placeholder="Retype password">
    <span class="glyphicon glyphicon-log-in form-control-feedback"></span>
  </div>
  <div class="row">
    <div class="col-xs-8">
      <div class="checkbox icheck">
        <label>
          <input type="checkbox"> I agree to the <a href="#">terms</a>
        </label>
      </div>
    </div>
    <!-- /.col -->
    <div class="col-xs-4">
      <button type="submit" class="btn btn-primary btn-block btn-flat">Register</button>
    </div>
    <!-- /.col -->
  </div>

routes.php

Route::get('/register', 'mainController@register');
Route::post('/registers','mainController@registration');

mainController.php

 public function register(){
    return view('register');
}

public function registration(Request $request){
    $username = $request->input('username');
    $email = $request->input('email');
    $contact = $request->input('contact');
    $password = $request->input('secondpass');

    $data=array("username"=>$username,"email"=>$email,"contact"=>$contact,"password"=>$password);
    DB::table('users')->insert($data);

    return Redirect::back();
}

Add CSRF token to the form:

{{ csrf_field }}

In Laravel 5.6+:

@csrf