Laravel 中的中間件是一種過濾 HTTP 請求的機制，用于在請求到達路由之前檢查或修改請求，或在響應返回瀏覽器之前進行調整。它分為全局中間件和路由中間件兩種類型，前者應用于所有請求，后者僅應用于特定路由。你可以通過 php artisan make:middleware 創(chuàng)建自定義中間件，并在 handle() 方法中編寫邏輯處理請求，如驗證用戶權限。創(chuàng)建后需在 Kernel.php 中注冊，并通過 ->middleware() 應用到具體路由。中間件可接收參數(shù)，也可分組使用，以實現(xiàn)更靈活的控制。使用時應注意保持中間件輕量，確保性能優(yōu)化。

Laravel middleware works like a filter for HTTP requests entering your application. It gives you a way to inspect or modify the request before it gets to your routes, or to alter the response before it’s sent back to the browser. Think of it as a series of layers a request must pass through — each one can decide whether to let it continue, stop it entirely (like blocking unauthorized access), or even tweak things along the way.

What is Middleware in Laravel?

Middleware in Laravel is essentially a mechanism that sits between an incoming request and your application logic. It's used to handle common tasks such as authentication, logging, CORS handling, and more.

Each middleware layer can either:

• Allow the request to proceed to the next layer
• Return a response immediately (e.g., redirect or error)
• Modify the request or response

For example, Laravel includes a built-in middleware that checks if a user is authenticated. If not, it redirects them to the login page.

You’ll typically find middleware in the app/Http/Middleware directory.

How to Create and Use Custom Middleware

If you need custom behavior for certain routes — say, checking if a user has admin privileges — you can create your own middleware.

To generate middleware:

php artisan make:middleware CheckAdmin

This creates a new file in the Middleware folder. Inside the handle() method, you can add your logic:

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

    return $next($request);
}

After writing the logic, register the middleware:

• In app/Http/Kernel.php, add it to either $middleware (global) or $routeMiddleware (for route-specific use)

Then apply it to a route:

Route::get('/admin', function () {
    // Only accessible by admins
})->middleware('check.admin');

Types of Middleware in Laravel

There are two main types of middleware in Laravel:

1. Global Middleware
Runs on every request. Useful for things like logging or setting up global session data.

2. Route Middleware
Applied only to specific routes. Perfect for role-based access control or feature toggles.

Also worth mentioning:

• You can assign multiple middlewares to a single route
• Middlewares run in the order they're assigned
• You can short-circuit the process at any point by returning a response early

Middleware Parameters and Groups

Sometimes you need to pass parameters to your middleware — like checking for a specific permission.

In your route:

->middleware('role:editor');

In the middleware:

public function handle($request, Closure $next, $role)
{
    if (! $request->user()->hasRole($role)) {
        return redirect('home');
    }

    return $next($request);
}

You can also group middleware for cleaner route definitions. For example, applying both auth and role:admin together under a name like admin.auth.

A Few Things to Keep in Mind

• Middleware should be lightweight — avoid doing heavy processing unless necessary
• Always remember to return $next($request) unless you want to block the request
• Order matters when stacking multiple middlewares
• Use middleware sparingly on high-traffic routes to keep performance optimal

基本上就這些。 Middleware 是 Laravel 請求處理流程中非常實用的一環(huán)，理解它的工作方式能讓你更靈活地控制請求和響應流程。

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