一、创建 middleware

php artisan make:middleware MustBeAnAdmin

修改生成的文件：app/Http/Middleware/MustBeAnAdmin.php

public function handle($request, Closure $next)
{
    if($request->user() && $request->user()->isAdmin()){
        return $next($request);
    }
    return redirect('/');
}

app/User.php 新增 isAdmin() 方法

public function isAdmin()
{
    return $this->hasRole('admin');
}

二、注册 middleware

app/Http/Kernel.php 注册 middleware

protected $routeMiddleware = [
    'auth' => \App\Http\Middleware\Authenticate::class,
    'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
    'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
    'admin' => \App\Http\Middleware\MustBeAnAdmin::class,
];

app/Http/Controllers/PostsController.php 注册 middleware

public function __construct()
{
    \Auth::loginUsingId(1);
    $this->middleware('admin');
}

三、测试

修改 app/Http/Controllers/PostsController.php

public function show($id)
{
    $post = Post::findOrFail($id);
    return $post->title;
}

访问：http://localhost:8000/posts/1，正常返回

修改 app/Http/Controllers/PostsController.php，登录 id=2 的用户

public function __construct()
{
    \Auth::loginUsingId(2);
    $this->middleware('admin');
}

访问：http://localhost:8000/posts/1，发现重定向到首页