Максим

init_vars(){
    $vars['x']='hello';
    return $vars;
});

$app->get('/[upload]', function ($request, $response, $args) {
    $vars= init_vars();
    return $this->view->render($response, 'upload.html', $args);
})->setName('main');

$app->get('/show_file/{id}', function ($request, $response, $args){
    $vars= init_vars();
    $args['fileUri']= $fileUri;
    return $this->view->render($response, 'show_file.html', $args);
})->setName('show_file');

$vars['x']='hello';

$app->get('/[upload]', function ($request, $response, $args) use ($vars) {
    $x = $vars['x'];
    return $this->view->render($response, 'upload.html', $args);
})->setName('main');

$app->get('/show_file/{id}', function ($request, $response, $args) use ($vars){
    $x = $vars['x'];
    $args['fileUri']= $fileUri;
    return $this->view->render($response, 'show_file.html', $args);
})->setName('show_file');