Silex allows you to run code, that changes the default Silex behavior, at different stages during the handling of a request through middlewares:
The application middlewares are only run for the “master” Request.
A before application middleware allows you to tweak the Request before the controller is executed:
$app->before(function (Request $request) {
// ...
});
By default, the middleware is run after the routing and the security.
If you want your middleware to be run even if an exception is thrown early on (on a 404 or 403 error for instance), then, you need to register it as an early event:
$app->before(function (Request $request) {
// ...
}, Application::EARLY_EVENT);
Of course, in this case, the routing and the security won’t have been executed, and so you won’t have access to the locale, the current route, or the security user.
Note
The before middleware is an event registered on the Symfony request event.
An after application middleware allows you to tweak the Response before it is sent to the client:
$app->after(function (Request $request, Response $response) {
// ...
});
Note
The after middleware is an event registered on the Symfony response event.
A finish application middleware allows you to execute tasks after the Response has been sent to the client (like sending emails or logging):
$app->finish(function (Request $request, Response $response) {
// ...
// Warning: modifications to the Request or Response will be ignored
});
Note
The finish middleware is an event registered on the Symfony terminate event.
Route middlewares are added to routes or route collections and they are only triggered when the corresponding route is matched. You can also stack them:
$app->get('/somewhere', function () {
// ...
})
->before($before1)
->before($before2)
->after($after1)
->after($after2)
;
A before route middleware is fired just before the route callback, but after the before application middlewares:
$before = function (Request $request) use ($app) {
// ...
};
$app->get('/somewhere', function () {
// ...
})
->before($before);
An after route middleware is fired just after the route callback, but before the application after application middlewares:
$after = function (Request $request, Response $response) use ($app) {
// ...
};
$app->get('/somewhere', function () {
// ...
})
->after($after);
You can add as many middlewares as you want, in which case they are triggered in the same order as you added them.
You can explicitly control the priority of your middleware by passing an additional argument to the registration methods:
$app->before(function (Request $request) {
// ...
}, 32);
As a convenience, two constants allow you to register an event as early as possible or as late as possible:
$app->before(function (Request $request) {
// ...
}, Application::EARLY_EVENT);
$app->before(function (Request $request) {
// ...
}, Application::LATE_EVENT);
If a before middleware returns a Response object, the Request handling is short-circuited (the next middlewares won’t be run, neither the route callback), and the Response is passed to the after middlewares right away:
$app->before(function (Request $request) {
// redirect the user to the login screen if access to the Resource is protected
if (...) {
return new RedirectResponse('/login');
}
});
Note
If a before middleware does not return a Response or null, a RuntimeException is thrown.