404 Not Found Handler

If your Slim Framework application does not have a route that matches the current HTTP request URI, the application invokes its Not Found handler and returns a HTTP/1.1 404 Not Found response to the HTTP client.

Default Not Found handler

Each Slim Framework application has a default Not Found handler. This handler sets the Response status to 404, it sets the content type to text/html, and it writes a simple explanation to the Response body.

Custom Not Found handler

A Slim Framework application’s Not Found handler is a Pimple service. You can substitute your own Not Found handler by defining a custom Pimple factory method with the application container before you instantiate the App object.

$c = new \Slim\Container(); //Create Your container
//Override the default Not Found Handler before creating App
$c['notFoundHandler'] = function ($c) {
    return function ($request, $response) use ($c) {
        return $response->withStatus(404)
            ->withHeader('Content-Type', 'text/html')
            ->write('Page not found');
    };
};
//Create Slim
$app = new \Slim\App($c);
//... Your code

In this example, we define a new notFoundHandler factory that returns a callable. The returned callable accepts two arguments:

• A \Psr\Http\Message\ServerRequestInterface instance
• A \Psr\Http\Message\ResponseInterface instanceThe callable MUST return an appropriate \Psr\Http\Message\ResponseInterface instance.

If you wish to override the default Not Found handler after you instantiate the App object you can unset the default handler then overwrite it.

$c = new \Slim\Container(); //Create Your container
//Create Slim
$app = new \Slim\App($c);
//... Your code
//Override the default Not Found Handler after App
unset($app->getContainer()['notFoundHandler']);
$app->getContainer()['notFoundHandler'] = function ($c) {
    return function ($request, $response) use ($c) {
        $response = new \Slim\Http\Response(404);
        return $response->write("Page not found");
    };
};