Laravel:未定义的变量内容

I have setup a Route:

Route::resource('conferences', 'ConferencesController)

Artisan therefore shows me a route:

POST conferences | conferences.store | ConferencesController@store

When I submit a Form from the create View, I get the error that a variable in my layout file has not been defined. Undefined variable: content is shown, nothing has been posted.

I opened my form like this:

{{ Form::open(array('url' => '/conferences', 'class' => 'conference-form')) }}

And finally, my store method in ConferencesController looks like this:

public function store()
{
    $validator = Validator::make(Input::all(), Conference::$rules);

    if($validator->passes()){
        $conference = new Conference();
        $conference->title = Input::get('title');
        $conference->description = Input::get('description');
        $conference->location = Input::get('location');
        $conference->plannedTime = Input::get('plannedTime');
        $conference->save();

        Mail::pretend();
        Mail::send('emails.conference.create', ['title' => Input::get('title'), 'location' => Input::get('location'), 'plannedTime' => Input::get('plannedTime')], function($message){
            $message->to('email')->subject('Een nieuw evenement is gemaakt.');
        });

        Redirect::to('/conferences')->with('message', 'Nieuw event is aangemaakt!');
    } else {
        Redirect::to('/')->with('message', 'Iets ging mis');
    }
}

How do I fix this error?

** EDIT: Added create method **

public function create(){
    $this->layout->content = View::make('conferences.create');
}

This should be really straight forward. In your views directory we usually have a folder called layouts where we put the page structure something like:

// default.blade.php
<html>
 <head> </head>
 <body>
   @yield('content'); // this is where your views will be loaded
 </body>
</html>

then in your case you should create a conferences folder and then a file create.blade.php in it.

@extends('layouts.default')
@section('content')
  // your forms etc
@stop

And in your create method inside ConferencesController

public function create() {
 return View::make('conferences.create');
}

And one last thing, when you try to send the email you should be passing an email address inside the to() function and you are passing a string