Noob Q: Laravel 5.4 - redirect()->with() - php

Question

I'm currently learning Laravel 5.4. I'm following a beginner's tutorial (we're on the same Laravel version).
In the video tutorial, the guy uses the following line of code in a controller:
return redirect()->route('posts.index')->with('error','Unauthorised!');
We both have the following in the view:
#if(count($errors))
#foreach($errors->all() as $error)
<div class="alert alert-danger">
{{ $error }}
</div>
#endforeach
#endif
The code works perfectly fine for the tutor on screen, however it doesn't for me - it redirects but doesn't pass the errors.
I used the following modified code in my controller and it worked:
return redirect()->route('posts.index')->withErrors(['error'=>'Unauthorised!']);
In order for me to learn, I need to know why the original code works for him - but not me? Like I said previously, we're both using the same version of Laravel.
Can anyone explain why?

Answer 1

I haven't seen the video, so can't say to as why his does work.
1.
return redirect()->route('posts.index')->with('error','Unauthorised!');
You redirect to the posts.index with a variable called error, and you check for a variable called errors so you could do it like this instead
#if(count($error))
<div class="alert alert-danger">
{{ $error }}
</div>
#endif
2.
You could support multiple errors like you other example and you could do it like
return redirect()->route('posts.index')->withErrors(['Unauthorised!', 'error_2', 'error_3', 'etc']);
and then you can loop through them as in your own first example (You don't need the keys in the array, but you can have them if you feel for it)
#if(count($errors))
#foreach($errors->all() as $error)
<div class="alert alert-danger">
{{ $error }}
</div>
#endforeach
#endif
3.
A third option would also be to use flash sessions, which is a session that only lives for the next request
than you could do
return redirect()->route('posts.index')->session()->flash('error', 'Unauthorised!');
and in your views
#if(Session::has('error'))
<div class="alert alert-danger">
{{ Session::get('error') }}
</div>
#endif
which I personally prefer as it gives me the option to just include the if statement in my "main layout file", and it will be shown on all the including pages.