我正在尝试理解Laravel 5中的中间件是如何工作的。我查看了中间件接口并理解到必须实现一个包含名为“handle”的方法的类。在“handle”方法中，会调用闭包。但我不明白，闭包应该传入什么参数。哪个类会调用我的中间件？它在底层是如何工作的？也许它像“foreach”，所有中间件将依次被调用？
更新：
我正在尝试实现自己的中间件：
interface Middleware
{
public function handle($request, Closure $next);
}
class MiddlewareCollection
{
private $middlewares;
private $request;
public function __construct(Array $middlewares, $request)
{
$this->middlewares = $middlewares;
$this->request = $request;
}
public function run()
{
$this->next(current($this->middlewares), $this->request);
}
private function next(Middleware $middleware, $request)
{
$middleware->handle($request, function($request) {
//How can I call the next middleware?
});
}
}
class FirstMiddleware implements Middleware
{
public function handle($request, Closure $next) {
echo $request.'first ';
return $next($request);
}
}
class SecondMiddleware implements Middleware
{
public function handle($request, Closure $next) {
echo $request.'second ';
return $next($request);
}
}
class ThirdMiddleware implements Middleware
{
public function handle($request, Closure $next) {
echo $request.'third ';
return $next($request);
}
}
$middlewares = [
'first' => new FirstMiddleware(),
'second' => new SecondMiddleware(),
'third' => new ThirdMiddleware()
];
$middlewareCollection = new MiddlewareCollection($middlewares, 'Request');
$middlewareCollection->run();
这样做是否正确呢？另外我也不明白在我的MiddlewareCollection类中，应该如何调用next()方法来调用下一个中间件。